Hi Dianna
I didn't have bleeding in second trimester, however a fellow co worker did from about 22 weeks. Turns out she has placenta previa. Every time she did a little bit of manual work she had a bleed. Now she has stopped work, she's had no further problems.
If this is the case, they wouldn't be able to diagnose without an ultrasound, so maybe for peace of mind you should request one.

Clare