cristina - a cross trainer is great. I have seen some success stories with exercise started only a short time before. If you have the time to commit to an hour a day (ideally 6 days a week) I would definitely add it to your sway, even 4 weeks out! You don't know if you will get pg right away anyways and then you'll be that much more ready for the next cycle. As for the OPK question, I'd try to BD that first night.
