Great news that some past challenges are getting resolved. Life is a big learning experience.
You need to recognise that at this moment, you are a perfect human being. You aren't messing up. You're simply discovering and experiencing new parts of your life and learning to better understand your reactions.
It does sound like you're still dwelling on your past relationships which didn't go too well. Those need to be removed from your current thoughts with this new guy as they tend to muddy the waters – by comparing to history.
When you think he's upset, both of you calmly sit down and try this technique:
LISTENING WITH LOVE
HOLD HANDS: Begin by holding hands.
LISTEN WITH COMPASSION: Your partner takes a few minutes to explain what is upsetting him or her while you listen quietly. As you lis- ten, smile and let your heart soften and ﬁll with compassion. Try to send loving energy to your partner.
REPEAT WHAT YOU HEARD: When your partner is done, you then repeat what you heard. Obviously, you do not need to repeat every word, just the main points. If you did not hear it all, repeat what you heard and invite your partner to tell you again whatever you have missed.
EXPRESS YOUR OWN FEELINGS: Then it is your turn to express what is upsetting you. Avoid engaging in an argument or attacking your partner. Simply describe what has been hurtful. It is important to express your hurt without getting defensive and without attacking. Talk about how you feel rather than what your partner has done. The more vulnerable you can be with each other, the more your hearts will open and the more compassionate you will be.