RH NEGATIVE

I am rh negative (o negative blood) and my boyfriend is a positive blood type. With our daughter I started spotting around 4 weeks and got the rhogam shot, then got the shot around 28 weeks and again after I had her. I *think* I had chemical pregnancies in March and April (was never confirmed but got faint positives that faded) and now in may I got pregnant! I’m 4 weeks today. I feel ok but I’m worried about needing the rhogam shot.. do I need it now? Or only at 28 weeks? I know if I start spotting to go and they’ll give it to me but is it necessary I should ask for it now or just wait until 28 weeks?