Blood test and mucus q's?!?

Amanda
I'm due for AF on October 17. Been ttc for 8 years just finished first round provera sept 8th due to not having a period in 2+ year. I started withdrawal bleed Sept 17. So waiting to see if I have ovulated on my own. Have a had an hsg test and laparoscopy this past week and everything looked fine. Glow predicted ovulation starting yesterday so we are going at it for the next few days then to the tww. My questions are my gyno has ordered a blood test October 8 said it had to be done day 20-22 of my cycle that started sept 17. What is for?? Also I do not understand about cervical mucus. I read you insert finger to check but I have had problems with this cause it's like I'm dry and have insert more than once to produce and do not know how to tell the difference in watery, sticky, whitish?? One last q.... Has anyone every tried the robitussin trick and am I suppose to take it or the hubby?!?