Can stress cause bi polar?

I have anxiety/ocd traits that I have had for years. My mom has exhibited the same traits as well as other members of my family. I know that with stressful situations anxiety can stand out the most and mine certainly does at these times. I have had an irrational fear for years of becoming bi polar. Logically I know that this is not likely as I don't have anyone in my family that has ever remotely showed such traits but I have been around a few and seen how erratic they can become and that frightens me so it's become an occasional obsession to worry about it (ocd nature). As far as lifetime stress goes I was involved with someone for a bit that was bi polar. I was young so I didn't understand the nature of the disorder or the severity at that time. After we stopped seeing each other he killed himself. I found out that he had tried to before I knew him. That stressed me out and made the whole anxiety/ocd thing a bit stronger I'm sure. I'm 26 now and that happened like 8 years ago. Could a stress event like that trigger something that severe even if I have no genetic predisposition. This is something that's annoying me a lot and I could use some reassurance.