Cramps advice

Need some advice on cramps. I'm 11w3d with first pregnancy. I work in retail so I do allot of waking, standing and stocking 9+ hours a day. The last few days I have noticed a dull pain on my left side after working 4ish hours. It goes away if i sit down for awhile but comes back when I get moving again. It feels like period cramps, just on one side. I have already seen baby and he/she is in the right spot (not on my tubes) any ideas what this might be? Probly being parinoid but hoping someone has some advice. Thanks 😄