Don't know why I am out of the age range for self harm but am finding that I do it more and more

I feel like I am an adolecent- alcohol and an argument with my husband when he is under the influence as well has resulted in me either cutting or burning myself. WHen not under the influence of alcohol I know I wouldn't do self-harm that would leave obvious scars-I just don't know understand my diagnosis of BDP as far as the SI goes why I only seem to do it under the influence of alcohol.