Clogged Well Drainpipe? Need a solution

I have a downspout that is attached to a drain pipe leading to my underground well. I just recently moved into this house and and connected an adapter from the downspout to the drainpipe because the previous one was put together badly (water was not really going into the adapter, but just falling out of the downspout). Since attaching this new adapter, it at first appeared as if water was moving into the drainpipe as it should be (during a heavy rain). I was watching it and then all of a sudden I noticed significant back flow and water pouring out of the top of the adapter. Does this mean I have a clog in the drainpipe? I don't know what the piping looks like underneath since I just moved in and did not put it together. Is there something else that could be going on? I need to fix this problem quickly because I keep getting puddles built up next to the foundation which is not good.