I agree with all of the others that you need to contact (1) a lawyer who will represent your intersts (2) a woman's help line that can provide you with more resources and advice on what to do in a situation like this (3) your local county prosecutor's office.....to file charges of assault and battery against your ex and (4) the department of children and family services, to make sure that your children's intersts will be taken care of. Also, you want to be on record that your meds are not affecting your parenting.
If you can't afford an atty, there are a number of free legal aid clinics that can help you. As to the woman's help line, they will help you to get the counseling and advice you desperately need.
If I were you, I would also file a complaint against him and possibly get a restraining order against him. Not only does it protect you (physically) but it also creates a case against him for abusing you. Any record he has will be evaluated by the case workers that are looking out for your kids. KWIM? If he is truly abusing you then he needs to be stopped. Don't do it yourself. Simply call the police or lodge a complaint against him.
Finally, as to DCFS, you want to make sure that they know what is going on, that you want to work with them to keep your kids and let them know all of your concerns regarding your ex.
Try to cover as many bases as you can. I know it is tough, but you have two very beautiful reasons to keep going....your kids. Get the help you need.
The last thing you should do, IMHO, is to sit back and take this. Even if you are not a "take-charge" type of person, enlist the help of someone, family or friends, who will help you stay on the path to clearing up this situation. Get someone on your side that will help you. Whatever you do, don't just let it go. I wish you the very best of luck!!
As always, we are all hear to *talk* to you too!