You’re not sure about your last confession:
If your last confession wasn’t very good, you might want to be careful about receiving the Holy Eucharist. When I say “wasn’t good”, I mean, if you willfully withheld a mortal sin, you’ve not been restored in grace. You need to see a priest, rectify the problem then you can joyfully receive Jesus. However, if you are scared of venial sins, even unconfessed ones, you needn’t stay away from Jesus. When you pray, God forgives your venial sins.
Even though the Church exhorts you to confess them in order that your sense of sin might be stronger causing you to avoid graver offenses with a little more ease. However, venial sins cannot deter one from receiving.
Glory be to Jesus…
How can the Holy Eucharist be dangerous to our immortal soul?
It is not that the Holy Eucharist is a danger to our soul. It is that we hurt Him when we receive Him in the state of mortal sin. The nature of mortal sin is so bad, that it results in our detachment from God’s saving grace. There are 3 criteria for a sin to be mortal (I found this from a response in Catholic Answers):
1. The sinful act must be grave matter, defined by the catechism in paragraph 1858 as a violation of one of the Ten Commandments
2. The sinful act must be known to be sinful
3. The sinful act must be freely chosen in light of the knowledge that it is sinful
This shows that we knowingly and willfully offend Our Lord, which hurts Him very much and stains, or even breaks, our relationship with Him. “The effect of mortal sin is to remove sanctifying grace—the life of God within us—from our soul. Without sanctifying grace, we cannot enter Heaven, which is why this sin is called mortal.” “As Saint Paul (1 Corinthians 11:27) tells us, ‘Therefore whosoever shall eat this bread, or drink the chalice of the Lord unworthily, shall be guilty of the body and of the blood of the Lord.'”
( Thought Co.: https://www.thoughtco.com/mortal-venial-sin-confession-and-communion-3970770 )
What if someone takes it, and they didn’t repent? I’m scared for the people that have done it.