If it carries on you should probably think about talking to a GP or someone. It's horrible trying to live with this feeling, it really is. Don't put up with it because you don't need to. Hopefully you are feeling better now but if not go get some help. :-)
Sorry no advice to give really but didn't want to read and run. You could be me really, even down to the house move before birth! My DDs are nearly 5 and just turned 1 and I too have felt similarly in the recent past. DD2 didn't sleep as well as DD1 and I felt a struggle trying to entertain 2 children during the day with totally different needs and wants and I think that definitely contributed to my down feelings. However in the past month or so DD2 has become mobile, easier to entertain and she loves watching and "joining" in with her big sisters games and it has become better. As far as your relationship with your DH mine is similar too, we just don't seem to have the time for each other like we used to, again I have put it down to the strain of having 2 children, we seem to have one child each a lot of the time and no-one gets time off! We had a really good chat a few weeks ago and realised we were both worried about the relationship but neither of us wanted out, we both still loved one another but were struggling a bit. Since then we've tried to make a bit of time when the girls go to bed when we sit and chat, no TV, Internet etc. this means we actually listen to one another and can chat about any issues before they get out of hand. We also are going to try to get my parents to babysit for a night soon to try to get out and have a bit of time just to be ourselves, not sure if that's an option for you. After saying I have no advice I seem to have managed to fill quite a lot of space, sorry, hope some of it helps.
I have a son who is two and a little girl who is almost 5 months, I have a beautiful new house moved in two weeks before she born. I have a new job to start in 6 weeks (Company Car, Great Salary etc), a great husband - who helps out loads but I am just feeling so fed up and not really sure why. I feel like I exist but not really living and feel like I have argued so much with husband lately that I am wondering if it would be better if we were to part (cannot believe I have actually written that), I am certain he feels the same. I feel that all I do is moan, I try to plan things for me and the kids to do when we are at home which I love but by the end of the day its back to the same sinking fed up feeling again. On the really bad days I just feel so angry about things. I did not feel like this with my son so feeling totally confused and angry with myself for feeling and behaving like this. Any advice??