Hi Sam, you are a DH! It stands for Dear Husband (you'll also see DP, DF etc, depending on marital status). Anything medical and formal will be listed in the board's glossary (bottom left of page) but the less formal include:
af (Aunt Flo) = period
pma = positive mental attitude (+ variations)
mc = miscarriage
edd = estimate date of delivery
+/- = positive/negative
I've a blank on anything else but I'm sure you'll have other replies.
Sorry to hear your recent attempt failed. As you'll have realised most of us have had at least one negative...take time to recover your mental and emotional strength and get ready for when your time comes.