Disrespectful Mother In Law

I can't stand my Mother In law, me and my Fiance have been dating for 7 years and just had a baby boy a year ago, now I am pregnant again and we were forced to move back in with his mother after a nasty flea outbreak in our new apartment. We are waiting for a chunk of money to move back out, but it has been hell since weve been here. Now ive always been a firm but loving mother, and take pride in feeding my baby healthy foods and keeping tv to a minimum. Im not a stickler but he is a baby and i see no reason for him to eat garbage all the time when he is so young. MIL is extremely disrespectful, constantly feeding him cookies, cakes, and candy. Hes on a schedule and she is constanlty throwing him off of it even after i tell her not too. I mean she tried to feed him cake when he was 2 MONTHS old. I nearly died. I wouldnt mind her giving him junk once in awhile but we are living there and its an every day thing. Now my baby is constipated all the time or has diarrhea from all the nast food she gives him. Hubby refuses to talk to her. She is always turning the TV on at all hours of the day. Everytime I try to parent hima certain way she will come in and pick him up immediately if she hears him cry. My once sweet little well behaved man is now turning into a monstrous brat! She gives him so much attention and coddles him to death and now all he does is whine and cry to be held. I am 8 MONTHS pregnant and I cant take it! PLEASE GIVE ME ADVICE!