AF??? Pregnant???

So Today is day 5 of being late. So I had called my Infertility Dr and spoke to 2 of the nurses. I explained to them what is going on, that Today is day 5 of being late and that I also have gained 10 lbs in a week, which is weird for me because I have had a problem gaining weight my whole life. I weigh 104.6 and that's the highest I have ever weighed in my entire life and I'm 21. So I dunno what is going on. They want me to come in asap Today because I am at such high risk if miscarrying, and they need to know when I'm pregnant asap. They are going to do a pregnancy test and give me an injection to make my period start. I have never had any kind of injection like that before, so kinda nervous. And if the test comes back that I am not pregnant, I'm gonna try my hardest to be strong, and tell myself I am doing IUI now so no need to be upset. But we will see how that goes. This all is just weird and I told myself I wouldn't get my hopes up, but I kind of did. I also have never had any problems with getting my period. I can always feel it coming because of how bad the Chronic Pelvic Pain gets [from the Endo] and it has gotten very bad as if I am starting, but nothing... I guess we will find out this afternoon. Sigh. I know whatever happens, happens for a reason.