Hang in there. The first three months are the roughest, I found, but after that it becomes a whole lot easier. My son turned three only two months after my daughter was born, and he literally rejected me when I came home with the baby! It was a little bumpy those first few months, and it didn't help that I wasn't getting much sleep either. I did my best to involve my son in everyday stuff, and when my husband was home and I didn't need to be nursing I would pass my daughter off so I could spend snuggle time with my son. I never quite managed to have both in my lap at once while nursing (the boppy takes up a bit of room, and we had a lot of trouble getting the knack of nursing down with her). It did help that we were supplementing too, as I didn't quite make enough milk for my daughter, so occasionally my husband was giving her a bottle. He also had hit the stage where he liked helping around the house, and I made a point of trying to let him "help" more often with little things, letting him know how proud I am of him and what a good big brother he was to help me.
It seemed like the three-month mark heralds a whole lot - the baby becomes more interactive, with smiles and giggles - which helps the baby seem more interesting to the older child. It was also the point for me when breastfeeding seemed to get a little easier and my daughter needed a few less feedings and they didn't take as long. Until that point, I think my son mostly thought of my daughter as a little theif - stealing all my attention away!
The cool thing now - my daughter is almost a year old and my son is coming up on four - they now play together! My son will sit down and show her toys and books and talk to her the way I do when I show her things. He's becoming a little teacher and playmate to her and it's wonderful!!