I completely recognize what you're going through because I went through the same thing pretty much PRECISELY when DS was 4 months old...so here we go...
Regarding weight loss: It is different for everyone (see threads regarding whether you lose/gain weight whilst/during/after a while of breastfeeding), but for me I also gained weight with pregnancy, but around six months of bf I started LOSING weight, even though I was actually eating more. Realize that when you gained weight during pregnancy it was your body preparing you for feeding your baby after it was born. You NEED that extra fat to sustain you and your bf child. For this reason, I would give it at least another couple of months of bf, try to be relaxed about the way your body looks (this is much easier for me to say now that I am on the other side of things, but trust me). I now weigh less than I did before I had my baby, and this is definitely due to bf. My baby is 11 months old, and, like I said, I started to notice a difference around 6 months.
Regarding relationship/sex: YES YES YES it is difficult to rekindle the fire when you do not have the biology to do it; it is HORMONAL. Estrogen is your "babymaking" hormone, and progesterone (which you need to make milk) is your "baby-caring-for" hormone. Not a lot of estrogen and lots of progesterone = NO SEX DRIVE. This is hard on both partners, but good on your partner that he hasn't pressured you or made you feel bad about it. What I decided one day was that one out of five times that my husband requested sex (you know, initiated it with pawing, or jack-russelling or whatever), I would accept and make love with him whether I was in the mood or not. I found that I could still enjoy the act while it was happening, it was just the initiation and getting into it that was the problem for me. So perhaps try something like that. I also felt that the release of sex did so much for me emotionally, and it certainly did a lot for our initmacy and closeness (even though, as I said, DH was only "getting it" one out of the five times that he "wanted it").
Regarding intimacy and your relationship: YOU ARE NOT ALONE. So many couples have a rocky time during the first year, particularly in those first months, because you are negotiating a new relationship among you. You are a threesome, not a twosome, and you're focused on your LO, understandably, because your LO needs more focus right now. But this gets easier as your child gets older, and more independent, then slides back a bit when separation anxiety kicks in because suddenly LO needs more attention again, (this is where we are currently), but I imagine that this also gets easier. Also, as baby gets older your partner can assist more in the care and comforting of the baby, making it more of a team-effort and something you do together rather than something you're doing for your baby and hence that your husband is not getting from you. My advice is to just be patient, and try to be as understanding as you can. If things continue to become more difficult, think of talking to someone. My DH and I finally decided, with mounting issues that were not being resolved properly, that this was the right choice for us (despite his initial reluctance to go), and it's helped tremendously.
And regarding your little baby: of course you want to put him before all of these issues, this is your biological imperative (see progesterone, above), and an emotional attachment your nurturing. You are obviously a wonderful mum and wife, you're just going through the growing pains that we've all gone through and it's rough, I know it is. DO TAKE TIME for yourself, and DO TRY TO TAKE TIME for your husband, and even if it feels like faking at first, try to have sex at least once a week or so. I know it sounds horribly mechanical and forced, but it will do wonders for the two of you in getting you focused on one another for a little while. It might be a quicky, and your LO might even have to be in the same room if you don't have someone to look after him, but he's too young to know the difference except that he will get the benefit of a very relaxed mum and dad afterwards
And the weight loss will either happen, or it won't, after few more months. My advice, and take it or leave it obviously, try not to notice your body or worry about the way it looks for the first year of your baby's life. At six months, maybe try a little exercise (you'll be far too knackered for that now), and at a year perhaps think of diet IF THE PROBLEM HASN'T SORTED ITSELF OUT, which it probably will.
I hope that is helpful. Good luck and remember that you're a beautiful mum whose just recently brought new life into the world, and your a wonderful wife who can manage to think of your husband and his needs even though you're the full-time carer of another human being. Good for you.
Hang in there.