Am 5'6. When I first joined the Navy I was just a short, skinny 18yo kid. Similar experience; was routinely ignored, talked over and disregarded. Became a gym rat, bought any and every workout supplement that caught my eye, and years later gained over 200lbs of muscle.

I expected women to take notice, but what blew my mind was interactions with other guys. Everyone wanted to hang out, invited to the club/parties constantly, and they actually listened to my input in social and professional settings. Basically became "one of the boys" at every command from then on just by being swole.

That primitive part of our programing that tells us big=strong=in group is so much more prevalent than we like to admit.