I would watch out and be very careful! In a situation like this (as in my own) He may just marry this new girl just to spite you and can very possibly take the child away from you if you do not continue to comply with these changes. The courts will look badly on you if they feel you are trying to hurt the relationship between the baby and it's father. It's better to try and get along with both the EX and his new girlfriend. If you don't, she may take her aggressions out on the child. Believe me it could happen! If you have a problem with whom picks up the child simply get it in writing as to who can pick up the child and enforce this at your day care or school. I suggest you take a look at California Family Code section 7600-7602 as well as CA Family Code Division 8 sections 3000 -3204Which may give you some guidelines to go by. I wish someone had told me about this before My daughter was forced to go live with her father.
The most important aspect in this situation is the child, and if the two parents can't see that then this child is in danger of being put in the middle. If you can't get along with your ex and his girlfreind, then you need to sit and have an adult conversation with them, maybe set some guidelines for them and you to go by, And let go of what ever old feelings there were in the past, and the hate that there is now. Believe me, it is easier to try and get along than to lose custody of your child and be in a depression as I was (and still am)
Go to mediation or sit down JUST the TWO of you, or write him a simulated agreement that he can sign- but don't put anything in there that you don't agree to, BUT you do have to compromise! Let me know if I have helped.
I wish you luck, and please read your Family codes, they can help you.