I have bad insomnia since stop taking prozac and seroquel (quetiapine). i can only sleep now if i take seroquel (quetiapine). is this because i stop taking prozac 3 weeks ago. will i be able to sleep w/o taking seroquel (quetiapine) ever?

Yes: You probably need to taper it rather than stop it cold turkey. Ask your doctor if he/she can prescribe alternative sleep aids.

Seroquel (quetiapine) withdrawal.: Seroquel has antihistamine (like Benadryl (diphenhydramine) has which is also very sedating). If stopped abruptly, it can cause antihistamine withdrawal and insomnia. If tapered slowly, (with smaller dose reductions over a couple of weeks), this should avoid this problem. Insomnia, due to anxiety or depression is a longer term issue. Discontinuation of an antidepressant like Prozac may contribute to this.

Consider Melatonin: With your doctor. Only means to getting regular sleep will be with a considered/ balanced approach with all of your medicines. Your doctor should help you choose what will work best.