BFP part deux- Rainbow after the storm

Well I retested with a FRER and got a very clear BFP!!! I'm completely shocked. We only had sex 3-4 days before O and that was IT! I didn't have any symptoms and quit temping halfway through because I was convinced I was out. I really hope everyting will be alright this time around. I have an appointment tomorrow with my OB and I know he'll order a beta and they mentioned giving me an ultrasound which I really don't understand because it's so early. I haven't even "missed" my period yet (AF is due Friday) but I'm sure she won't be arriving. I'm only about 3W4D according to my LMP and my estimated due date is 4-25-14 (my birthday is the next day). This is the best present ever! Praying for good news tomorrow. I'm getting my rainbow after the storm possibly, and I'm elated!