Christmas if he doesn't want anything serious then he may well not want much to do with the child, however, he may be willing to support his child financially. What does the father of your dd do? Does he have no input at all, not even financial?
I can imagine it must be very scary.
Remember your boyfriend doesn't have the right to push you into not having the child.
Nor has he have the right to take over.
You may hope for him not to be too involved and if he doesn't want to be involved then this may suit you both. If you do not want him to be involved and he does want to be involved then as the dad he would have some rights, but I think you would need to work out what worked. (Sorry over use of the word involved!)
Maybe someone else can advise on that. I've not had that experience.
My only concern is that at some point you need to really put yourself first and do what you feel is right for you. I've no idea what that is in this situation. You started this when you chose to have your dd and face your mum's wrath. Well done.
So carry that on, and I think you need to decide what you want, your needs seems to be pushed down below the needs or desires of this man you hardly know; your mum and wider family, who treat you very badly; and even your dd, and although as a mum I know we always try and put our kids first but the decision to have another baby, or not, is not normally one left to the decision making of a five-year-old.
I really hope you can access some counselling to enable you to feel at peace with whatever you decide.