This is definitely NOT okay. Incest is not something which can
be taken lightly.
I'm not exactly sure what you mean by 'things have been getting out
of hand', but if it is what I think it is, then both of you need
professional help. Pronto. Seek a professional counsellor. I'm not
sure what we can really do to advise you here. You may try to
excuse your actions by saying that it helps alleviate depression -
but the way I see it, those actions of yours are contributing to
the depression.
It's normal for a parent and child to show affection for each
other, but when sexual thoughts are involved, that is really,
really abnormal.
