God’s grace is the only way we can repent, so yes we still can receive graces while in a state of mortal sin. God is incredibly generous like that.
One thing to be careful of though - and this is something St. Ignatius of Loyola wrote about in his Spiritual Exercises - is that when we are in mortal sin, we basically are in the devil’s camp. What this means is he will be trying to keep us from repenting by giving us comforts and even some joys so that we feel no need to repent. Comforts that could even feel like they are from God. Which is frightening to be honest, but from experience I know it’s true.
Not trying to say this is what is happening in your situation, since I don’t know the details, I just wanted to mention that. We have to be careful when we are in mortal sin because the devil is going to use all his tricks to try and keep us there. That’s why it’s best to get to confession ASAP.
Bottom line: yes we can receive graces from God while in mortal sin, but these graces are always meant to lead us to confession and repentance.
Will keep you in my prayers.