I was in a similar situation and we went through IVF to have our bubba.... It makes it that much harder when it's so sudden like this, and that you're pregnant and he takes off. Extremely difficult situation and I'm sorry he did this to you.
It's still very early days. What I found though is that I slowly started to get used to a new routine and gain my independence back. Now I don' miss him at all and don't have any interest in meeting someone new. I'm actually a much happier person than I was before. A new partner would be a major inconvenience to me and DS's life now!
I can't tell you how long it will take to chase away the loneliness birds, but I CAN tell you you will absolutely get there and will feel so much better then! These feelings are temporary, and lets face it, it can't get worse it can only get better!