Back off the Rogaine or anything else until you know more. Besides having your thyroid checked as others note, consider seeing a dermatologist.
One question, too: Do you wear your hair back in a ponytail or bun or chignon or just otherwise pulled off your face with barrettes etc. much or most of the time? Daily, or many days in a week?
Wearing the hair pulled back all the time can actually cause a form of alopecia that is directly related to having the hair pulled back too much of the time. Dancers get it -- they wear their hair pulled back so much that they can develop permanent "bald spots" along the hairline (the bangs area that you mention). The hairline actually recedes and it can be a permanent change, and while letting the hair rest from being pulled back can help, you might need more serious intervention.
So -- if you do wear your hair back a lot, even if it's not super-tight, I'd start wearing it down, or in a loose side ponytail, etc.
My daughter dances and tends to have to have tight buns for several hours most days in the week and also wears a ponytail daily for school (just her choice). But recently we read in a dance magazine about this condition of the receding hairline/hair loss related to pulled-back hair. Then she went to a new hairdresser who said she herself has seen her own hairline moving back and hair falling out due to wearing ponytails and buns etc. all the time when she was younger, so she started letting her hair "rest" from those styles. The hairdresser recommended moving ponytails around to different locations on the head (a low, loose side pony instead of one right at the back of the head, for instance), doing softer styles if the hair just has to be pulled back, etc.
If that's not your issue and you don't wear your hair back much or at all -- no worries! It's just something I wanted to mention, since it sounds like the thinning is right in your hairline or bangs area, and that is exactly where this hairstyle-related thinning can take place.