You're not alone and it doesn't mean you're a bad mother for feeling this way.
Yes babies do tend to grow to look more like their mums as they get older. What also helps - I do admit to slightly encouraging my DS1 to choose hairstyles etc which are nothing like XP would have worn and clothing which is different as well. It really upset and unsettled me recently when my SIL bought him some clothes which were similar to the kinds of things XP would have worn (not on purpose - she is lovely DH's husband it's just that she happened to buy those kinds of things) just seeing him in them. I'm not awful - I didn't say anything, ban them or take them off him, but I mentioned how nice he looked in some other clothing, and after a reasonable time had passed so the connection wasn't obvious, bought him some things which I knew he'd like but were quite different in style. It worked and the novelty of the newer things outweighed the other items I was less keen on. We had a clear out and they were among the things he chose to get rid of. And other things that he still keeps aren't quite so bad because he has so many other clothes he rarely wears that exact combination together. Obviously if DS1 was really dead set on a hairstyle which happened to look like my XP I wouldn't forbid him, but I do feel more comfortable and that he's more like "himself" when his hair is a bit longer.
Something else to bear in mind over the coming years as you heal. It can be common for abusers to behave in ways which are typically childish. That means that during normal phases of childhood development, your child may replicate behaviours that your abuser used to do. Also when frustrated, tantrumming etc they can commonly replicate facial expressions, etc, which are related to traumatic memories for you. This can be frightening for an abuse survivor, not because you are afraid your child will abuse you, although you may automatically react in a victim role rather than a parental role, but because it brings up the fear that the child may grow up to be an abuser himself. Rest assured, this is extremely unlikely. You've removed your child from the abusive environment and they won't have that daily input any more. Even if they have contact with their father the effect of that role model will be many times diluted by your model of a calm loving home. If you find this affecting you a lot I liked a book called When Your Kids Push Your Buttons. But generally it's just something to bear in mind - children don't act like abusers, but abusers frequently act like children. The difference is that children can develop empathy and learn that they are not the centre of the world as they grow and develop normally. We don't know exactly what makes abusers abusive, but we generally believe that it's at least highly influenced by their environment/upbringing. People don't become abusive thanks to genetics alone. If you do find yourself reacting in a victim or childlike role towards your child when they are still young, seek counselling and/or parenting support (classes?) ASAP - it's important to get a handle on how to react in a calm and firm adult way.
I also totally agree with the point about babies not having much personality so people tend to focus on their looks, and that as you start moving into the toddler years you'll find that their personality really comes out and it helps define them as their own person.