Sian

Hi i have a lenovo g550 and i have never had a problem before. the computer itself appears to function normally. its just when i type it keeps adding 1's in wherever it likes! its incredibly annoying. any ideas? if i ty1pe w1it1hout deleting 1it loo1ks like thi1s or much worse and sometim1es it goes off by i1tself adding1 line1s and lin1e11s of one1s :( please please help