My child won't sleep through the night at age 4!?

I seriously don't know what to do. We've sabotaged her in some ways. I know this. First, she slept in our room until she was 18 mos. old because we had no choice. She had her own bed and we didn't go to bed with her, but still. She was sick for the majority of her first three years, so more often than not, we soothed her to sleep. About three months ago, we started putting her to bed without us in the room and that was going well, though we've never had problems with her GOING to sleep...just staying asleep. She was getting it. She was only waking once a night. We'd put her back and she was fine. Then three weeks ago she got sick again. She's better now, but she's waking 3-4 times a night and screaming bloody murder if one of us doesn't stay with her...mainly me. She's become ten times more clingy with me than she EVER was. She won't even take a bath without me being in the bathroom as opposed to just daddy. She won't use the bathroom, go to any other room or let me leave the room without following. I'm getting literally 3 hours of broken sleep a night. She goes to daycare and likes it, but where I used to be able to give her a kiss and say "I'll see you this afternoon.", now she cries when I leave, and hangs on my leg until I literally hand her to her teacher. It's killing me! My husband does take her back to her bed so that I can get at least some sleep, but she still wakes several times. Nothing traumatic has happened to her, except that she was home with us for a week solid when she got sick, but it's been almost two weeks and she isn't getting past this separation anxiety. Any advice?