Am I being selfish for asking him to have his 6...yes that's right SIX children over every other weekend?

My boyfriend and I have been living together for almost two years. About a year ago, he started having his children over every other weekend. I must say, he has six children, which for me, and only child with a VERY small family is a LOT! Then he wants to have the boys (his two boys) over the other weekends in between. Well I am 7 and 1/2 months pregnant, he just had knee surgery, and with the economy the way it is, money has been VERY tight to say the least. When his children leave, there is very little left in the kitchen and since he is only getting workman's comp., most of the expenses have fallen to me, which I have been paying the bills the whole time anyway because over 55% of his income goes to child support anyway. I have no problem with them coming Saturday and going home Sunday every other weekend, but he wants them to come Friday and go home Sunday and it's turning into at least two being there EVERY weekend. I must also mention that I have a son who does live with us, but is that not different since he lives with me? I just feel like he's asking me to put his kids in front of mine when their mothers aren't forced to do that.