Hi firstly congrats,i would insist on progesterone pills or suppositries.especially due to previous history,why havent they given it to you ?..
If you found out you were pregnant 4 weeks ago you would not be 5 weeks.
All that aside, you need to insist on progesterone supplements or you will probably miscarry. Progesterone is necessary to sustain pregnancy. It keeps the uterine lining from thinning out until the placenta takes over the production of progesterone (10-12 weeks).
Please tell your doctor to put you on progesterone, prefarably by injections. Low progesterone may indicate that there is a problem which may complicate your pregnancy. Since you had good results previusly, there should be no problem convincing your docotr that indeed progesterone may do more good than harm