How can I fix my Durabrand 7in portable dvd player?

Well, I bought this dvd player a while ago but i used it for only 2 months. I cleaned the lens yesterday and the dvd player is still telling me the disk is invalid. I tried different ones. I even used the original ones that used to play on it but still nothing. Sometimes, the cds work, but they skip too. I dont know how to fix it. Can anyone help?