Hi, I'm confused on why my periods seem off. One month they will be on the 20th, the next on the 11th. Will this effect trying to conceive? 19 female

It happens. Periods can be irregular for a number of reasons. The key to pregnancy is whether you are ovulating during all the cycles. If there is any question, check in with an ob/gyn and they can help you out.
Yes. So your periods are not regular. And more of a problem is that your cycle are very short. So you need to be evaluated first to make sure that the problem is not because the ovaries are failing. Then your doctor can confirm to see if you are ovulating. Even at 19, if your periods come every19 days, you will likely need fertility treatment. But first and foremost you need a couple of tests\.