Well first off, you have had some good advice on here so I won’t knock that. I agree, pray, go to mass and confess your sins often. God loves you very very much and wants you to go to heaven. Anyone who tells you anything else is lying and is most likely listening to the devil, simple. No one, can say whether you or your family are likely to go to heaven or hell, so don’t try to guess. Only God will decide and even then only when they die. Read St Faustina’s Diary as it tells you a lot about God’s Divine mercy and you will not be afraid again. It is a long book though, 600 pages…
2 other things, about the mortal sin, ask God to help you get out of it and stay out of it. Who else is going to help you? Be serious, get down on your knees and beg him to help you, admit to him all you bad parts and why and wherefores and beg and plead for him to help you stop. He will help you. Every Time you fail, seek His mercy and start again. Second thing, dont assume your priest is so busy he can’t help you, ask him if he has any advice for you or if he can bless you in your endeavour to stop this sin or even if he’ll pray for you. Or if he can recommend anyone to help you. It is unlikely he has not heard of these issues before. Be a warrior for God. Have you tried sacramentals? some Holy water around your home to help you when you feel tempted? praying the rosary when you feel tempted? Make the sign of the cross too. A particular saints medal may help? Could your priest come and bless your home? God bless you, I will pray for you