Swollen ankles/feet on herceptin, anyone?

My feet and ankles swell but not always. Some evenings I can't see my ankle bones and my feet look like balloons and other evenings they look normal. I do pretty much the same things every day (sit in front of my computer) so that doesn't account for it. I've been on herceptin (every three weeks) for six months and this comes and goes, as does my cough. I'm wondering if anyone else on the board has experienced this type of swelling and, if so, did you notice a pattern: did it precede a lower LVEF? Does it happen immediately after infusion, or a week later, or two weeks later? Does it come and go as mine does. I'd love to figure this out and would appreciate hearing from anyone having similar problems.