Unexplainable Screen Problems for my iPhone 3G

I have had my phone for more than a year. The other day I woke up to use it and in the upper right corner there was a series of dots on the screen. (I did not drop the phone recently, I did drop it a couple of times a couple of months prior, but at least 4 months from a drop and this problem). I tried to power-off and restart. When I did, in addition to the dots there was a line streaking from right to left about a 1/4 inc. long. I used the phone a usual for the rest of the day. Overnight the battery died and I recharged it. When the power came back on, I had the dots, the line and another line. After two more days, I have four lines and the series of dots.
Has this happened to anyone? Does anyone know the cause? And most importantly, does anyone know how to fix it?
Thank you.
iPhone 3G iPhone OS 3.1