Oh dear, don't worry too much I know it's harder done than said, but if you go in for regular check ups and doc says everything is OK, then everything is. I didn't feel my little guy til about 21-23 weeks and u was worried just like you, soon you will be able to feel him move around and wiggle and you will feel so happy! Try to be patient :) <3 congratulations!
I am 32 weeks pregnant and I didn't feel my baby move till about 2 months ago so maybe at 20 + weeks I would say you're fine when I Went to ultra sounds baby was always moving but I wasn't feeling it..
I didn't feel my baby move until like 22 weeks. They sell Doppler's at babies r us that are useful also!
I'm on my 3rd pregnancy and I didn't feel any movements till 18/19 weeks, some women don't feel them until 22 weeks. Try not to worry, if your being told that everything is fine with your baby then it is. I do agree with the above post tho, try not to skip meals even if your just eating a small snack of fruit, it all goes along way.
Some peolple feel them sooner than others, do you have regular prenatal check ups?
If dr says baby it's ok, don't worry and take care of you and your baby and don't skip meals, I don't feel any humger too but I try to keep bags of salads and fruits on my fridge so if it's time to eat and I don't feel hungry, I make a little salad or a bowl of fruit, yougurt also helps you and your baby ;)