help!!

so my little guy is 9 months old he will be 10 months in two weeks for the past 3 weeks he will not sleep at night he is fighting his naps also. before this he was a great sleeper he went to bed at 8 every night and slept til 7 the next morning. now it's so hard we still have the same routines nothing has changed so I'm confused as to why he will not sleep now. he finally falls asleep between 12 and 1am and is up at 7 he will only take a two hour nap during the day. he just will not sleep! I have almost called his Dr to get him looked at but I just didn't know if this is a stage or what. do you ladies have any tips or advice to get him sleeping again?? thanks in advance!!