Progesterone question

I am on progesterone suppositories for the first time. I go in tomorrow morning for a blood pregnancy test, but I'm not feeling very hopeful as I've had no physical signs and only BFNs when testing at home... Do the suppositories delay my period? I've had no sign of AF either, so I'm confused. today is CD 28, and I'm very regular. 
I'm also concerned that IF the suppositories do delay AF, how long after I take them will I start? I'm leaving for a mini vacation Wed-Sat, and my doctor will want me back in for baseline testing somewhere between CD1-4. Our 10th anniversary is Wed, so I won't delay the trip for a visit. I may just have to take next month off I guess...