I take it you left your partner? I'm sorry you couldn't work things out, but that doesn't mean that you can't both be fantastic parents seperately.
Are you still on anti-depressants for the PND? They really won't mix well with alcohol, as I'm sure you aready know.
Are you eating properly at the moment? if not, that could cause sickness ad dizziness. I know that with a little one to look after, food maybe the the last thing on your mind at times, but it is important to look after yourself.
Pinktwink made some really good suggestions - you've been through a lot, so maybe you do need to go back to your GP or HV and be honest. The mother and baby groups could also be a good idea, in my area there is one specially for mums who are under 23, and it could be a way of making new friends as it sounds like your mates don't really understand what you're going through. I know it's a cliche but having kids changes your life, your priorities and you - I don't think that anyone without kids can fully appreciate that.
Do you get out much during the day? I work in a college part time but during the 10 week summer holiday I began to feel like I couldn't cope with my little one - we were both snapping at each other, because we were stuck in the house all day everyday, just the two of us and we were both bored, as soon as we went out and did something (even simple things like taking our dinner to the park or walking around the block) we started to get on much better again!
Anyway enough of me rambling! Hope you're feeling better soon x