HELP!!!! IP address & mail id forgery//spoofing

Hi all

I have been presented with some mails apparantly sent using my mail id and IP address of a public computer (cyber cafe) I often visit.

I am 100% sure neither I nor any one from that cafe sent that mail.

ppl who claim to have received those mails harbor severe ill will against me... and I am pretty sure they mounted a man in the middle type of attack. They are tech savvy and seemingly trained in this type of tasks... regularly monitor mails and log ins of ppl... and I have detected sevral spying things on my system.

I urgently need to stablish who, how, where and when