DNA testing…..

Our dcda twins were born on 5th November and are doing great. However I’m still struggling to tell them apart. The only difference is twin 2 has slightly pointier ears. My whole pregnancy I found really hard to believe they’re non identical because we were trying to get pregnant for so long and my partners sperm isn’t super sperm. So for him to impregnate me twice in one night so to say after years of trying seems really hard to believe. I know 30% of dcda twins are actually identical just an early egg split which I think is the case with us. So how do I go about getting the dna test done to find out? I know it won’t change anything but I think it’ll be nice to have a definite answer.