on going constipation

I am a 34 year old female.  I have not been able to have a bowel movement on my own in 2 weeks. I don't even feel like I need to go but I know that I do since it can be over a period of 2 or 3 days that I haven't.  My stomach will hurt sometimes but i don't feel that bad.  The only thing that helps me go is milk of mag. and then it is diarrhea.  It helps enough to remove what is in the bowels but then I do not have another bowel movement until I take it again and it is the same results.  I have tried a naturel laxative and it didn't help at all then a herbal colon cleanser and it made me sick- i felt like i had the flu with diarrhea.  I am not sure what to do.  I feel like I will never be normal again.  what can be causing this and any suggestions on how to remedy it?