PLEASE HELP !!

My baby was born on 29/01/2009 and weighed 3160g. At 2 weeks he weighed 3360g, 3 weeks 3570g, 4 Weeks 3600g and today, 5 weeks 3590g. We started off well and I was really please when he gained 210g in a week, but since then it has been downhill.

I was really shocked and upset last week when he only put on 30g and it was so much worse today when he actually went backwards. I don't know what to do!!

My first two babies weren't breastfed - jaundice and really bad nipples but I expressed and they had supplementary formula feeds, so this breastfeeding is new for me.

I thought we seemed to be going really well - he has good feeds, has heaps of wet nappies (even pees through huggies), settles well after a feed, feeds (on demand) every 4 hous but sometimes goes up to 6 hours, boob is noticably empty after he feeds and he looks like he is growing and is a really good baby.

Everyone I have spoken to says to put him on formula, but I am enjoying breastfeeding him (except for the not putting on weight part) and I would like to continue but not at his expense. I feel like I am starving him and that I am failing him. Milk supply is in no way a problem I have heaps and heaps.

Has anyone had a similar experience?? and what do you suggest??