Mom Guilt

Ok I got the mom guilt going. I have a 5 year old son and a 4 month old son. Last night my 5 year says to me, "Mom how come you don't play with me that much anymore". AHHHHHHHHH What is a mom to say. I feel so bad. I just told him that I now have to give some of my attention to his little brother, but I will try  to play with him more than I have in the past couple of weeks. So now I am trying my best to play when he asks.