It's really possible that this other woman is using stuff on him (that is, hoodoo) to keep your boyfriend around. Especially if she's got access to his clothes, food, and bodily fluids, she can trick him.
Does he ever come to your place or leave clothes there? If so, you can get a pair of his worn underpants, tie them in a knot (to tie up his nature so he can't "perform" with any other woman) and bury them in the front yard of your place (to lead him back to your place). If you don't have a front yard because you live in an apartment, get a potted plant and put it near the front door and bury the underpants there.
Get some Lucky Mojo Cast Off Evil Sachet Powder and Bath Crystals. If he ever leaves clothes at your place, wash the clothes and add a pinch of the bath crystals to the rinse cycle; that will "dress" the clothes. Pray that as he wears these dressed clothes, all evil associates and habits will go away from him. Dry the clothes as usual and give them back to him, and BE SWEET when you do; I know it'll be hard, because he's been an ass, but just be like "Oh, hi; you left these here so I washed them for you" *wink wink*
Take the Cast Off Evil sachet powder and lightly dust the inside of his shoes, if you can get to them, or sprinkle some on the pathway where he walks, and pray that he will leave these women and drugs and come back to you.
Also, make a honey jar on him; put your name, his name, the name of the child you have together, AND "Unborn Child" to represent your current pregnancy in it. You want to sweeten him back to your whole family too, not just you. Light pink candles on it daily and dress them with Reconciliation Oil and Return To Me oil. Wear both oils as perfumes on your body whenever you talk to him or see him.
And most importantly: take care of yourself. Ask your friends to pray for you. Make sure you rest, eat nutritiously, don't drink alcohol and don't smoke (hey, I'm a nurse; I have to say it
). Stay calm and balanced for YOU, and trust in your own work.