I Had A Tatnus Shat 20 Months Agon. I Want

I had a tatnus shat 20 months agon. I want take tdap shot but my doctor said that when i got tatnus shot, it was most likely tdap cause since 2009 there is only tdap and no more just tatnus shot and if i get the shot again, i will have a wild reaction. my daughter is having a baby and i don't want baby harmed in any way