Thermostat in my car was changed and the temp. gauge still rises, what can my problem be?

There are a lot of different things that could cause this: clogged radiator, bad water pump, problem with the AC compressor, and many more. There isn’t enough information to give a good diagnosis.
The fact that the “service engine” light is on means that the engine computer has detected a problem and is giving an error code. Your car has a port into which a machine can plug to read this code. If you can get that code it might provide insight as to what’s wrong with your temperature. It’s a good idea to get it checked anyway, so that the engine doesn’t blow up.

Mine is doing the same thing.
I’m going to have to take it in and have it looked at I guess. Ugh.
I totally can’t afford to do that.

@Katniss I don’t know how much it costs to have the codes read, but you can do it yourself with an OBD reader. They cost about $20 to $200 depending on bells and whistles. Then you can lend it to @marciarned so he can read his too!

Or you could donate it to Geek Group for community use.

probably the radiator, take it to a shop and just have them look at it and they will tell you the problem for free. The solution to the problem will be expensive so if you know anyone who can work on cars, see if they can help you fix it. The local shop wanted to charge me $800 to replace the radiator in my BMW within 2–3 days….fuck that, my boyfriend found one for $80 and replaced it himself in 1 hour.

You can have the codes read for free at any Advance Auto Parts. Here is their store locator Advanced Auto Parts . They will lend you the tool or help you do it if they are not busy. (I try to buy something I will use later as a way of saying “thanks”. (windshield washer fluid, oil, etc.) Usually their tool is always up to date with the latest software.

There might be air in your coolant system that needs to be bled out.

I like @RocketGuy‘s suggestion . When the engine is cool fill up the radiator. Or have a garage fill it

My fancy Prius engine started throwing overheat codes after it left a repair shop. They had to call in a Toyota technician to show them how to bleed air out of the system. Works fine now.