O blood and pregnancy!! Help a stressed out first-timer

I'm 22.3 weeks. All my life I believed I had ab blood. The doctors always told me that from when I had surgery when I was 6 to when I had to get stitches because I fainted and busted my head. I went to the doctor on the 6th and she told me that I had O negative. She then told me at 28 weeks I'm going to have to get a shot of RhOgamma to make sure my antibodies for my blood don't flow over and affect my baby.

She also said I'll have 2to receive another after birth. And if I was to start bleeding like a period while pregnant I would have to get one then too. She said something about if I would be about to have more kids afterwards.

No other woman in my family has O so I can't really ask my mom or my sisters because they wouldn't know...

I'll be 19 in a couple weeks and I never thought I would have to worry about not having any more babies this young

Are there any moms that have O blood and had to receive the shot? Do you have more than one kid? Me and my husband want 3 more after we have our little girl and it's really stressful to think I won't be able to have anymore babies because of my blood.