1. You dont have to guess, CD1 is the first day of true menstural bleeding so just take it ont he 3rd day of bleeding. Your problem is you havent had a period for a while and you need to be on one to take the clomid, perhaps discussing enducing a period with a dr would be a good first step.
2. Thats a very general assumption that you will ovulate on day 14 ohh dr's love that blinking assumption after the bleeding stops make love either every other day or on average 3 times a week.
3. Nothing really to be aware of, clomid can cause headaches and moodswing as well as a basket full of minor side effects, do watch out for severe pain int he pelvic regeon as clomid can cause large cysts on the ovaries.
best of luck my love

baby dust to you
Sa xXx