I think your feeling baby movements :))))!!! Mine feel the same way and completely shocked me THE first time I felt them...try something sweet or something cold and see If the movements come again
It could be the baby...im 18 weeks 3 days and feeling mine moving around here and there...nothing strong yet but definitely feelin him...it could be gas as well or muscle spasms...you could try drinking something cold then sit down for a while and see if you start feeling anything.
I also feel little twitch like movements and jerks every once in a while but when will I feel something to reassure it really is kikking, the type that makes your belly move on the outside and puts a big smile on my face?