how do you know..?

How do you know how long you have been infected with lyme for? I have seen people say their dr's estimate they've had it for certain amounts of time.. I became symptomatic in August, but how do I know when I actually was bitten by the tick and that it wasn't dormant in my system? I had an IGM positive for lyme and babesia, and IGG negative (however 2 of the bands were positive and one IND for lyme IGG) (through Igenex)-- this was also after 2 weeks of antibiotics given to me by another dr because of one band of positive IGM on a lab corp test, but he still believed I had it... (LUCKILY)