5 year old boy that is obsessed with hair.

I have a 5 year old son and he likes girls ever since he started preschool he's always talked about having multiple gf's but for some reason lately he's been talking about him wanting to be a girl I ask him why he says because he really wants long hair I said if it's because of the hair we can just let your hair grow out but he says boys don't look good with long hair. He does have 2 Barbies and he doesn't care about dressing them up all he cares about is their hair he will put them in water and flips their hair back and forth. My SO makes comments at times saying we should throw him a Barbie birthday party and that pisses me off I see that as bullying I don't think our son is gay but even if he was it wouldn't change the fact that he's my son and I would love him and support him 100% percent regardless of his sexual preference. My dad told him he was going to stop loving him if he saw him playing with Barbies that pissed me off as well because I feel that's something cruel and stupid to say to a little boy. Anyone else going through something similar????