I have the same issue and it sucks. I'm definitely very sympathetic as I am always picked on for my muscles!
Example: I tried a dress on today, showed my friend & he said I looked like "a chiseled piece of steel". Um, that is not what I want to hear whilst wearing a dress! In his defense, he thought he was giving me a genuine compliment.
I get told that I have the body of a boy. It doesn't help that I was recently quite sick & lost a fair bit of weight so any curves I had previously do not exist anymore. That one bothers me A LOT. I can deal with everything else.
As for the clothes: strapless dresses are a no-no with broad shoulders/back. Cardigans are great if you can stuff your arms inside. Loose, 3/4 length sleeved shirts look cute & feminine too, as long as they're not baggy. As of today, I have given up completely on dresses that are not strechy/smocked in the back. Strechy jeans are your friend. I like the Artist jeans from American Eagle because I don't have to worry about my calves busting out, since the bottoms "flare out".
As far as stores go, I find American Eagle to fit decently. Hollister and Aeropostale are probably the worst for us muscular chicks.
Side note: someone said "your calves are big" & I replied (without thinking, I am not at all mean spirited but I hate it when people comment on my body) with "so is your risk of heart disease". Whoops.