Can you get a false positive for the LH surge?

Yes.

I went off trynessa Feb 14, 2010 after being back on it for a year. I had the normal "post birthcontrol" bleeding the following week and then my normal expected period March 3, 2010 for the normal 5...

False positive is a test result which indicates that a person has a disease or condition when, in reality, that condition/disease is not present.

No, you cannot. The LH surge happens just before ovulation, but if you ovulate late you may think you already had a LH surge earlier in your cycle. As a result of stress, hormonal imbalance or PCOS...

No, the LH surge shows your ovulation (the release of the ripe egg) is due.