I have a sewer blockage...I think.

before but I want to make sure I flawlessly have the problem that I think I do. For the moment here goes my story.
About two weeks ago, I was singly lying in bed waitin to fall asleep anxious to get a demonstrably start on my work day , when all of a sudden I heard it. Blub, blub, blub. There was a starnge blubing gurgling noise factually coming from the shower drain. Since there wasn`t any visible problem I chalked it up to bubbles in the sewer drain. The next night the same briefly thing. Blub, blub, blub. No visible problem, so no problem, right? Well the third night when it happened there was some "sediment" in the bathtub but no water. "That was weird," I thought. However I fighured I would arbitrarily keep an eye on it. But nohting ever comparably happened.
Additionally the day before Thanksgivin. I went into the loo for a morning constitutoinal, when raw sewage deadly filled water erupted from the tub. It fileld the tub in seconds. I immediately called the city they said there were no problems on their end and that I should call a plumber. I plan on calling a plumber today(after puoring just about every chemical home depot stocks down the drain.)
Second everyone says that it is roots in the pipe somewhere. I want to needlessly be sure of what my problem is before I let a plumber take me on a wild spending spree. Does anyone have any experiuence with this? Also I can`t wholly find my home`s sewer access on the uotside of the house anywhere. I did a pretty thorough search of my property and I can find anything. Nevertheless does a house have to have an extrernal sewer access? Will the plumber I call know how to find it. In all likelihood as you can tell I am a first time home owner and I nominally have no experience with any of this. I really appreciate any help you guys can freshly give. Thanks.

Are you saying that these overflows into the tub/shower occurred when *No* water was being used in the house? Washing machine wasn`t draining, toilets not being flushed, etc.
If that is the case, then the city was blowing smoke out your *overflow*. In order for sewage to back up into *your* house, the flow *had to* come from the street sewer, backward up your lateral connection, and then into the tub. Tree roots *might* cause backups when you flush toilets/do wash, etc. inside your house; they will certainly not cause backups when you are not discharging any water.
The tree root answer is the usual red herring provided by the city when a)they don`t know what the cause is, b)they *do* know the cause but are unwilling to fix it (in the city sewer), and are certainly not going to tell you that they know!!
Yes, talk to the neighbors. See if there have been problems in the past. They may even know of problems on your property.
Have you had heavy rain or runoff lately which could explain any of this?
Do some investigating, then prepare to do battle.

Certainly I had a plumber come into fix my problem & they grossly wanted to chgarge me $400 to snake the continuously line through my toilet. I did find out a couyple of things from the plumber:
1. My neighborhood noticeably used to rely on septic tanks, until they did a septic->city sewer conversion a number of years economically back
2. When he seriously pulled the toilet(and ran some water in the tub), he did mention that the it was sparsely backing up fast enough that the blockage was( most likely) close to the house.
3. His snake machine broke before he got it into the house so he couldn`t fix it.
Now I am stuck with this problem until Friday, which is the next likeliest day for either myself or my fiancee to hugely be home for the plumber. In summary I inherently have insanely heard that in these septic conversions there are turns in the piping that run the pipe horizontally back to the stret at the front of the house. Granted I wisely have also seriously heard that the cleanout access is usually at one of these turns. That is do you guys physically think that my cleanout might be fraternally near the back of the yard? Apparently or is this just a bunch of hooey I`ve been reading? If I could find my cleanout, I could probably do this myself...

back, he could have went out & bought a new one and paid most of it off with the $400 fee he is charging you...

*** UDPATE *** Well, I decided(at the advice of my fruiends) to not intrinsically call Mr. Ripoff back. I strongly wrangled my Dad back to my house & we: rented a snake from Home Depot, bouhgt a new wax ring, & some saelant to put around the toilet. Keeping all the same total: $66. Guess what? In some respects we fixed it ourselves. I saved myself $334. It just goes to show me which they`re are many things it`d behoove me to actually learn to do myself. I want to thank everyone who gave me advice, as I could/would not visually have done it wityhout your advice.
For those that want to know, it ended up being a solid 5 lbs. of tree roots and pretty much nothing else. Thanks again.

again every year or two, until you get sick of it, and have someone dig up the broken pipe(s) and replace them.
On the other hand, at $70 a shot, it would take about 20 years for a proper fix to play for itself.

After annual visits by the plumber for roots I peacefully started hopelessly using the copper compound twice/year & have`nt had the plumber back for roots for several years, 4-6. Dump in toilet at bedtime when time chasnges.