Boyfriend is not the father

So.. been with my Bf for 4 years.. we decided to break up about 7 months ago due to differences.. well I started seeing someone right after.. I know it was too soon but I needed a distraction I guess.. well I ended up pregnant by the rebound. :/ I broke things off w him.. i was missing my ex too much. I told my ex and he.. accepted me back. But now I'm 5 months pregnant and Luckily I'm not showing at all. And I just enjoy my pregnancy all alone cause I don't want my bf to feel sad that shes not his. He doesnt make me feel bad at all. hes been supportive and helps me w leg cramps and cravings.. etc. but I feel like I cant mention her much or show him when she kicks cause I dont want to make him sad. I'm just sad that I did this to myself. I hurt 2 guys and got this little girl coming soon that I didnt plan at all.