tink - make sure you research yourself what the levels mean. Some doctors would say that my level (US 6.5 on my 3rd clomid round- 10 is normal for a natural cycle and 15 is normal for a clomid cycle but anything above a 5 means ovulation) was too low for some doctors to consider it to be ovulation on Clomid, but I KNOW I ovulated (OPKs, temps, period, cramps etc). Also, if you ovulated late before, day 21 might have been the wrong day for the bloodwork. It can be off a day or two but must be near 7dpo.
This time, it looks like you'll be doing it right on time.
If you have low progesterone, there are several different kinds of supplements... the most effective seem to be vaginal suppositories (I took them last month when I thought i'd gotten a positive test and it brought my temp right back up and held off AF).
Doctors differ on when they'd want you to start them... mine won't let me have them until after a BFP.. some doctors put women on them after ovulation.
Higher doses of clomid can increase your progesterone by getting your follicles bigger or making more eggs... but there are risks and my doctor wouldn't up my dose because he said all I need is to ovulate, that increasing it wouldn't help.