Why can't I cry anymore? whats can i do to make it happen again ?

i used to cry all the time and now i cant anymore. im not sure whats wrong with me, i get tear ducts most of the time but i cant simply, just cry. its so weird. im usually depressed. have very few friends and kind of shy 95% of the time. i smoke weed to get me happier and cigarettes on a very rare occasion (i know it isn't a good thing) aaand i used to join sports but now i don't feel like i actually give a crap about it anymore. nothing matters to me as much as they used to. im not sure what im supposed to do. i always feel like i want to cry but just cant! ive tried sad songs like what hurts the most - rascal flatts and movies like the notebook, nothing gets out except tear ducts. i've also tried thinking of bad memories, breakups, someone dying or leaving me alone. nothing works!! i want to know how to cry so i can remove all my pain out of my body and feel a little better after. please tell me anything how to cry, just simply anythingg would help. im not sure if its blocking in me but how do i cry again or unblock it lol ?