The expiation for sexual intercourse while fasting is to fast two months consecutively; if one cannot do so, then feeding sixty poor persons.

This expiation concerns sexual intercourse with one’s lawful spouses.

Yours is an even more grievous a sin. So, firstly, you need to seek sincere repentance and beg for the mercy of Allah and expiate it by fasting two months for each day you have broken; in case you cannot, do so by feeding sixty poor persons. On top of these, you should follow it up with as many good deeds as you can. Allah says, “Good deeds wipe out the bad.” The Prophet (peace be upon him) said, “Allah does not wash out evil act through evil; rather He washes it out through good deeds.”