hiii dear i admire you for positive outlook no need to postpone your marriage it is just anxiety. fear and stress will affect sexual health. still you don t have experience in sexual intercourse so by time you will learn how to maintain erection it is common in initial relationship it is just your fear and fear will lead to anxiety and you got frustrated this is vicious cycle so you need to understand and calm down certain factor can affect in erection and try to modify it 1st is life syle stress and busy life style make u fatigue and secondry to this it makes less desire in sex and erectile problems 2nd is relationship free communicative and mutual understanding will help sex is mutual act so try to do mutually and tell your problem to partner this will reduce your anxiety and able to erect easily so stress free lifestyle and mutual communication will help psychological soundness is must. so basically no need to worry. it will get best when time comes just want to be relax. prostate do not affect erection abdominal pain might have some other course so need to evaluate further get well soon thank you