If my lmp says i am 7wks preg, is it possible to only be 5wks?

Yes: It is perfectly possible that your ovulation was little late in the cycle. There are some ways to tell if the current pregnancy is normal. Hcg levels should about double every 48 hours. These can be measured by blood tests. Also, a scan of the pregnancy in one to two weeks should confirm the fetus' growth and presence of a normal heartbeat.