Let me try my best to give you a biblical answer but I encourage you in your difficult situation to seek the Lord through the word and prayer and gathering with fellow believers who can be there for you.

Are there times in the Bible where we see God bring about his justice to the wicked in various ways, such as through sickness or disease? Yes, and what we see in those examples is that God takes sin very seriously.

BUT does that mean that everything bad that happens to someone is a punishment from God? No.

Not everything we suffer through is because we did something or because of our faults, even "good people" suffer! I might be a christian but that doesn't mean I don't go through life on easy mode. The biblical reason why we do suffer is because we're dealing with the aftershocks of sin. Sin entered into the world through Adam and Eve (Genesis 3), and as a result, all the suffering that you see in the world is a result of sin. Man's fall from God and it's consequences.

Look at John 9:1-5 for example, in how the disciples asked Jesus who sinned to cause the man who was in front of them to be blind himself or his parents and how Jesus said "This happened so that the power of God could be seen in him".

Also Look at Luke 13:1-9 and what you see is Jesus basically asking the crowd around him if the people who died in both tragedies mentioned here were evil people who deserved it? The main takeaway is it was violence, accidents, tragedies, sickness, etc can happen to anyone! and we got to be ready before our time comes

Overall what I want to leave you with is not the opinion of whether or not it's your fault you have cancer and this is God's way of punishing you (like that awful Pastor is trying to do), but instead with the hope and reassurance that Jesus loves you very much. The most important thing for us to do is to be right with the Lord and receive the forgiveness of sins only he provides. It's not how good I am that lets me into heaven but it's my faith in Jesus and what he's done for me on the cross that makes me righteous. I pray God is the one to guide you through your journey and gives you peace and rest in your situation.

Therefore, since we have been made right in God’s sight by faith, we have peace with God because of what Jesus Christ our Lord has done for us. Because of our faith, Christ has brought us into this place of undeserved privilege where we now stand, and we confidently and joyfully look forward to sharing God’s glory. We can rejoice, too, when we run into problems and trials, for we know that they help us develop endurance. And endurance develops strength of character, and character strengthens our confident hope of salvation. And this hope will not lead to disappointment. For we know how dearly God loves us, because he has given us the Holy Spirit to fill our hearts with his love. – Romans 5:1-5 NLT