If you had no family history of baldness, then I would say you are most likely getting your mature hairline. However, based on your age and family history, I would assume that you're in the early stages.
What should you do?
1: Talk to your doctor and get bloodwork done. There's a 98-95% chance that you'll be perfectly fine and suffer no sexual side effects. If you're in the unlucky 2-5%, then you have a 98% chance of being just fine if you stop treatment. However, that bloodwork will serve as a baseline that you can try to return to in the unlikely situation that you get long lasting side effects. Think of it like life insurance. You're VERY likely to not need it, but it would suck if you didn't have it.
2: Finastaride, at least .5mg every day
3: Nizoral shampoo.