I am 21 weeks and baby has been moving a lot for a few days now but today she doesn't seem as active. i'm a high risk pregnancy so i'm worried!

See your DOC: How long you don't feel baby's movement? Feeling excessive movement followed by a period of silent is usually normal but as you are a high risk pregnancy you should always check with your obstetrician who knows your pregnancy well & will able to assure you or will evaluate you.

Simple answer: Call OB right away and follow their advice. You may need to go to the office for a non-stress test or you may be asked to go to labor and delivery for assessment. Either way, decreased fetal movement is considered cause for concern so call OB now

If she moves: at least 3-5 times in a n hour she is ok.