Rachie,
Didn't you just start zoloft? It could definitely be the meds that make it difficult. It's called emotional blunting and it's a common side effect of anti depressants. Hopefully, it should even out after a while but do discuss this with the doctor who prescribed your meds. I also have had times when I couldn't cry but now I'm a regular leaky faucet!
It must be very frustrating though.
Take care.