Fertility treatment (ICSI)

Myself and my partner have been trying for a baby for the last nine years we have been told my partner has very weak sperm and his chances of getting me pregnant naturally are very slim. We have tried everything except ivf but nothing has worked. I heard about Intracytoplasmic sperm injection (ICSI) which sounds ideal and would give us a 90% chance of conceiving a baby. We are not eligible for free treatment as I have a 15yr old son but my partner has no children of his own my son was 7 when my partner moved in with us we asked about ivf treatment but were told we would have to pay for this which we simply cannot afford. We are both hard working people with full time jobs who are longing to complete our family.