Hey Angel,

Um did you happen to post in the wrong forum by mistake or something because all the symptoms you listed can go along with thyroid problems.. But everything you said sounds more like depression...

If it was thyroid, you'd more than likely have other symptoms and problems.. like always cold, dry hair falling out, dry skin, theres a list under the sticky link at the top of the forum....

And you might not like my opinions but you asked..

I gained 50 lbs. in a matter of months with little effort.
You said you had depression and it "went away"..So if you mean it went away because you are or were on meds.... THAT is why you gained 50lbs. But even if you weren't on meds, weight gain can also be either a thyroid problem or depression.

constantly depressed
Thats understandable when you gain 50lbs.....
I have tons of trouble concenrating.
erm that could be either I guess..
Cannot get pregnant.
Don't even want to know why on earth you're trying to get pregnant at 17...Not for nothing, but that could be depression related.cause some ppl think if they have a baby they'll feel better... But anyways, As for thyroid, people with thyroid problems can get pregnant. But you also say you have really messed up periods, if your bodys that messed up, it might be too messed up to get pregnant right now too...
Totally bizarre periods.
LOTS of things can throw your period out of wack. You're age could still deffinetly be the reason. Stress, change in diet & exercise, any kind of medication..ect.
Lack of interest in things
Um another depression symptom..

Unless you have other symptoms you haven't mentioned, I don't see why you think its your thyroid...