I am a medical marijuana patient n I been trying to get pregnant for over 2 yrs. I know people that got pregnant smoking so what's wrong with me?

Don't smoke if preg. If you contemplate pregnancy, don't smoke mj or tobacco. They cause harmful effects on the fetus. Mj is associated with chromosomal breaks, prematurity and learning disabilities in fetuses exposed to it in utero.
Curious? Perhaps the issue that requires marijuana treatment may also interfere with conception. Tubal motility could be affected by these cannabinoids, and metabolic abnormalities could also be problematic. I'd suggest you seek consultation with a fellowship trained reproductive endocrinologist to evaluate the entire range of fertility factors that might be involved.
Hard to say. It is hard to get good representative research data on this subject. Either you or your partner may have ongoing fertility issues regardless of your habit. Evaluation through a fertility center is reasonable. In my state the kid of such a pregnancy would be placed in foster care and you would face charges of child endangerment. Consider the possibilities if you continue to smoke MJ.