im scared , think im pregnant..

ive been seeing this guy for a couple of months.....i done a test about a month ago or maybe longer... and had a urine test done at the hospital and they came back negative ...ive been having periods regular but ive had sexual intercourse with him again lately without using anything and its its been about 3-4 weeks since we last did...and ive been feeling flutters in my stomach just above my belly button, my stomach also looks as if its growing a bump...ive had acheing back pain ...my bottoms even been acheing..am i pregnant??