It's early days hun. Let yourself grieve the end of the relationship and then you can start moving forwards. If it's meant to be, it will work out. If it's not then you have to accept that and start planning for your future. Pining over him and thinking about him being in another relationship is not going to help this situation or help you move forward.
I'm 22 weeks and just separated from my OH this Sunday just gone. It's hard but I'm also relieved, the relationship wasn't working out and it was making us both unhappy. Now I can focus on me and being the best person and mother I can be. It's daunting, but totally possible.
Good luck xx
Re: 15 weeks pregnant and partner has left me..
Seriously. Something in his behaviour is off. The guy sounds like bad news. You're better off. Seriously what kind of a skeezebag manslut screws around and then kicks his pregnant partner out because (he claims........) she's not 'getting over it' fast enough? You don't need his lies and STDs.