Rubella

I went to my obgyn last week for my annual exam and she mentioned for my to get tested to see if I'm immune to rubella since we are trying to get pregnant. I got a call today from the doctor stating I'm not immune and to recommend for me to get my mmr vaccine before we get pregnant. I was going to wait until my expected period which should be coming next week if  not pregnant already. I don't want to go to the dr to get the vaccine just in case I'm already in the early stages of pregnancy. Have your Drs told you about it? Should I go ahead and get it now or wait until I get my AF just to be sure?