Thank you for the question. I assume that by"major trust issues" you mean difficulties trusting people in general, perhaps because of bad experiences in the past.
The Bible makes it clear that every human being, with the exception of Jesus Christ, is flawed (Romans 3:12). Our natural tendency is to seek our own interests, and sometimes even when we want to do the right thing, we lack the power to carry it out (Romans 7:18). That doesn’t mean that no human being is trustworthy, or that we always do the wrong thing, but it does mean that it is all too easy for us to hurt one another or let one another down.
God, however, is completely different. He is 100% dependable and trustworthy (Psalm 9:10; Isaiah 26:4). The Bible often emphasizes how God can be trusted in a way that human beings can’t (e.g. Psalm 118:8-9).
That doesn’t mean it will necessarily be easy for us to trust God, but it does mean that we should try not to allow human failings to rob us of the comfort of God’s dependability. Sometimes we need to pray, like the man in Mark’s gospel who was let down by Jesus’ disciples and so struggled to trust Jesus himself:"I believe; help my unbelief!" (Mark 9:24).
Learning to trust God comes by getting to know his trustworthy character and track record of faithfulness to his promises. So it helps to read from the Bible regularly (daily, if possible) and to look for reasons to trust God. Read through one of the four gospels, for example, and notice how the writers often quote from the Old Testament to show that God’s promises are being fulfilled in Jesus. Or read Exodus or Joshua in the Old Testament, and notice how God keeps his promises and rewards his people’s trust. In the psalms the writers are often calling on God to help them because God has helped them in the past. (e.g. Ps 71:1-8)
One thing to add is that when we rely on God’s promises, it’s important to make sure that we’ve understood them correctly and how they apply to us today. Sometimes people feel let down by God when they think (sometimes through the influence of well-meaning Christians) that he’s promised something which he hasn’t, such as healing from an illness or success in a business venture. We need to be particularly careful in translating promises from the Old Testament to today, since they’re sometimes specific to a particular situation.
I hope this is helpful, but please let us know if it doesn’t answer your question or if you’d like to ask a follow-up.