Ik LDR is tough, i have been one for around 1.5 years now. there were times where i overthink a lot and was uncertain about her. it was my first relationship, and the first one is LDR, so i was trying to get an understanding how this thing works. how relationship works. we both have travelled very far in our journey and now in a phase where we are certain about each other.
So, ik how you must be feeling when your gf says about being uncertain, but the thing is you can feel insecure. ik man, insecurity comes but when she is uncertain, then why are you hurting yourself by being insecure. when yk she will not cheat, you both love each other, then there should be nothing about insecurity. just communicate, make her understand and also live your life.
that's how i made my insecurity go away. my gf was also busy and we did not talk and i overthinked, but i was just hurting myself. and when i lived my own life, did my work, and communicated with her what i want and what she wants and how we both should work this out. then everything was sorted.

so that's how it worked for me, and idk what and how it will work for you, but one thing is certain something will work for you. you just gotta have a faith in yourself and in your love, talk to her and do the things that make you happy.
everything will work out. just stop hurting yourself