GUYS: why is this guy doing this? What do I do about it? Total mind f*ck?

This guy and I have been good friends for 4 years. He's 4 years older. For about 18 months we talked and flirted and I harboured a massive crush on him and really wanted to be with him, I wasn't obvious to him about it but I'm sure he knew that if he asked, we'd have gone out. When turned 18 he seemed to reciprocate, my friends started to notice too. However, he moved away so wasn't home much and saw each other less so I decided to get over it and concentrate on being friends.

We stayed in touch, so managed to keep the friends thing going. Then he got a gf and I got a bf. Since getting with my bf, whom I love and is complete at utter proof that I'm over this other guy. However, this guy still periodically messages me but it's no longer friendly but really flirty. I don't reply. He messaged me a couple of weeks ago saying he'd had a 'rude' dream about us. I just left it. I was on holiday with my bf at the time and didn't want to encourage the behaviour. Yesterday, I found out his gf is pregnant and due at the end of the year. Something, I'd have thought he'd have gone on about on social media as he's quite active on there but no. Anywho, it made me feel guilty about the things he's been saying to me, should I tell someone? Or is keeping on ignoring him best? I just feel really mean on his gf and now child :/

Thanks for reading and thanks in advance for any advice.