Ha! I finally figured out the identity of this plant. It is related to geraniums, and called cranesbill. I have been reading a gardening book and the description of one plant sounded familiar, so I looked it up for an image. Mine is growing much better since I moved it to be in shade near the front porch. It got leggy after flowering; I cut it back and new foliage has sprouted. I really like it- hope I can encourage it to spread, propagate it or just buy more next spring.