Yes, doubting or suspicion is a sin, especially when you know the truth,the fourth Commandment is honor your Father and Mother ,respect them for what they are,i think you need to say the forgiveness prayer each day or make an examination of conscience each night before you sleep,they may be possible childhood hurt feelings which by prayers and surrendering everything in the hands of Jesus each day or during Mass will be of help ,ask Jesus to pour his precious blood on your mind body and soul and heal your wounds etc,God Bless
Sirach 37:10 Do not consult the one who regards you with suspicion; hide your intentions from those who are jealous of you.
1 Timothy 6:4 is conceited, understanding nothing, and has a morbid craving for controversy and for disputes about words. From these come envy, dissension, slander, base suspicions,
James 1:2 My brothers and sisters,whenever you face trials of any kind, consider it nothing but joy, 3 because you know that the testing of your faith produces endurance; 4 and let endurance have its full effect, so that you may be mature and complete, lacking in nothing.
5 If any of you is lacking in wisdom, ask God, who gives to all generously and ungrudgingly, and it will be given you. 6 But ask in faith, never doubting, for the one who doubts is like a wave of the sea, driven and tossed by the wind; 7, 8 for the doubter, being double-minded and unstable in every way, must not expect to receive anything from the Lord.