Puberty advice needed!

My almost 13 year old son has started to go through puberty. I have noticed he gets aroused by the strangest things. Like he watches you tubers playing other video games or life hacks and he gets super figity and is constantly touching down there. I have always been a single momma and yes I know how to go about birds and the bees with him, but he doesn't really seem interested in a relationship and he has also told me he feels he is gay which is totally fine. I am just not sure how to start this conversation he has been SUPER moody and always snaps for no reason lately other than the hormones I guess. So just looking for tips tricks things others have done when talking to a son being a single momma. I am tired of this monster he is becoming and have to find a way to get him to talk without feeling shy or he is doing something wrong.