Cramps while standing at work today.

Today was my second day of work at the job I've always wanted working with animals! I am 23 weeks pregnant and today when I was working after about 2 hours of standing I started to get a strong cramp in my lower abdomen. My baby wasn't kicking or anything but it hurt so bad I asked to get a stool to sit down and do my job. So they let Me. I'm not used to standing I usually lay around during the day. I figured it was just my body because I haven't been very active during this pregnancy. Has anyone else experienced this?