I have AP, but

my background is chemical engineering. Do you think Iwill have a trouble to come back? I changed my visa in US, so no stamp on my passport. My I-140 is still waiting. I checked some website and it seems that I'll loose my status if later my I-140 is rejected. I have got my AP and EAD already. What do you think? Am I safe if I want to go back to China this winter?
Again thank you so much!