How to find more and potential bugs?Thanks?

I'm working as a mobile software tester for a couple of days,now i just found a few bugs and all of them are not severity.The most thing that let me upset was some bugs i didn't make them reproduced,but my colleague can do.I really don't know why,maybe the main factor is myself.Now i feel nervous and think if testing really fits me?Anybody who is a tester could give me some valuable tips.Thanks