This has happened to me with both of my pregnancies now - right at the end of nine weeks/beginning of 10 weeks, my nausea slowly disappeared and then one morning I woke up and realized it was totally gone. I'm still tired and crampy, but definitely not as bad as I was the first 10 weeks.
I've heard that at 8-10 weeks your HCG levels start going back down, which can mean that your 1st trimester yucky symptoms start going down too. In my case, that seems to be exactly it since 8-10 weeks is when my symptoms have started lessening.
Obviously, my first pregnancy where this happened resulted in my DD and I just heard the heartbeat at 10.5 weeks for this one, so loss of symptoms can mean no issues. That said, get checked out if it makes you feel more comfortable of course.