No u have nor gone beyond a mature hairline in my opinion. In fact youd struggle a man that does not recede further than that in their twenties. (oviously excluding non- caucasians, and the odd freak that has his hairline in the middle of his forehead, )
The best indication of whether its male pattern baldness is signs of miniturization. Such as rows of hairs on the exterior of the hairline that r miniturized, but be aware that all hairs can be miniturized after they fall out and regrow in the mormal cycle. U should be looking for entire rows of miniturized hairs.
Whichever the case though, at the moment ur hair is fine, so i'd go live ur life now, because if u find out later u do have male pattern baldness, u will regret not making the most of ur junior years.
just my opinion though.