it must be very distressing for you, along with everything else you have to contend with? Have you seen a specialist about it? I'm not expert on ED, but I know there are several treatment forms you can try. But, answering your question: usually, any medication you can take before an amputation, you can take afterwards. Having said that, you may have to wait until your scar is well healed?
Try not to worry too much about the amputation. I've been through elective amputation and it's not nice

, but there is an end to it.
Take care