Im 16 and had protected sex with my boyfriend, but I have had 2 UTI's. My weight is a little high but its always goes up and down. I have back aches but I've had back problems before. I was also 2 days late on my period and when I got it I ended it a day early. I can't talk to my parent's because they would kick me out. I don't know what to do. I can't tell if it's my mind playing tricks on me or if Im really pregnant. PLEASE HELP!

The only way to know is to take a test. And whatever the result of the test is, take it as a lesson not to have sex again until you are actually prepared for a pregnancy. The only 100% effective way to prevent pregnancy is abstinence.

Could it just be stress causing these symptoms?

You're not really having any pregnancy symptoms. You mentioned your weight tends to go up and down and that you sometimes have a sore back anyway. The UTIs could be from the sex. Periods can be a little off now and then... even more so in the teen years.

As justcurious mentioned, the only way to know for sure about a pregnancy would be to try a pregnancy test. Certainly if you have sex, protected or not, pregnancy can be a possibility. See what happens when your next period is due.