Need some advice, my mans friend hit on me

So right now me and my babies father are having some problems and aren't together with a label, however we are both loyal and still fuck around and we get along and raise our kid together, I just have some trust issues I need to work out and I've been so busy with my job same with him that it's hard to always just focus on us. So we both agree to just take it slow and work on being good parents and work on our trust.

Anyway, I met his best friend who lives in a different city than us a few times. They are our only other parent friends. His best friend is engaged and has a son. We've stayed up there for thanksgiving and Christmas and a few other times just for fun.

His friend asked him for my contact information because I do marketing and he has a company and needed some advice. I've helped him and he's helped me via email and we've been helping each other out with work.

I posted a photo on instagram and his friend emailed me saying my butt look nice and then continued the email with work stuff. I tried to just disregard it and reply to the work part and then when he responded he told me "I broke the internet with that one".

Once again I ignored it and then a week passed and I posted a photo with my hair changed. He emailed me saying it looked good and he noticed the change and then wrote work related stuff.

I don't know what I'm suppose to do. I haven't replied to the comments but I feel uncomfortable. I know his fiancé and even though we aren't close and only talk when we see each other I would never want to have her think anything

And I love my child's fAther and I feel like his friend is kind of disrespectful. What am I suppose to do? Do I tell my babies father? I don't want to make a big deal about it because I don't want my babies dad to get mad. He has a crazy temper and he might even blame me. And I also don't want to risk the girl and the guys relationship, they have a son. I feel stuck and weird. And now I'm working with the guy. Ugh help