Anice, I honestly think your stress level is creating alot of problems for you.
More so than you realize. I don't think you are able to relax, therefore, your body is staying knotted up and this will help create pain. It will also cause the pain level to stay on the rise. I am afraid your nerves are close to being shot. All of these negatives things you have going on around you really does have a very negative effect on your recovery.
In all fairness to you at this point, I think if I were you, I would request that the husband limit the visitation to a day visit where he can take the kids somewhere else for the day, not at your house, until you are on your feet better. You need to be expending energy concentrating on things you can do to get yourself over this hump-you do not need alot of distractions. This is just nuts what you are going thru and putting up with-enough girl. In fact, Iwould be having this conversation with him this evening-he needs to understand your health needs better.
So, I take it that he thinks its ok for those kids to be disrespectfull to you? If thats the case, he needs to take his kids and leave, sorry. I never tolerated that kind of crap. I had a step-daughter that the daddy thought did no wrong, she was mean as a snake. By the time she got to jr high she was kicked out school. I did not take any crap from her or him when it came to his daughter. My own children did not act that way and I sure was not going to put up with someone elses doing it. If he can't understand that, then he would be out with me. I flat was not going to allow her to be a bad influence on my own children. Are you telling me that ever since you had surgery his kids have been at your home every weekend? Thats insane!
I have a newer model for a TENS unit and I love mine. Not only does it help with the pain, but helps with muscle spasm. In effect it can work a muscle without damaging the muscle.
Time is your friend on your recovery. It will get better it just takes time.