Hello cautious, firstly congratulations on your pregnancy.
Four years ago I was in a very similar situation. My H upped and left with no warning whatsoever, and within days I discovered I was pregnant (we'd been actively trying for 3 years). Turns out he'd left me for an OW, who was also pregnant (though she was more pregnant than I was, it was very messy to say the least).
I had minimum contact with him during my pregnancy, though it was very stressful as we also had to do mediation and I started divorce proceedings. All contact from me was via a solicitor - expensive, but helped me keep sane and on a relatively even track (whenever he communicated with me he somehow found ways to blame me for everything, as they tend to do).
I'm now sat here with my 3.5 year old. I'm single, work 3 days a week, DS goes to nursery. It's been hard - the first 2 years were really hard work to be honest, but it IS getting easier as he gets older. My family and friends have been great. I ended up getting our marital home with some financial help from my parents. I have control over our future, our money, what we do, what we eat, where we go (I realise now I didn't have much control in my marriage).
I wish you all the best. The most important thing is these first few weeks is you manage to rest and take care of yourself and your pregnancy. 
If you need any further advice please PM me.