The phrasing of your question sounds like "if your girlfriend is having a b1tch and moan session, should you ***** and moan as well?" Don't participate in those. If she tells you her problems, just listen. Cheer her up a bit and carry on.
If you have something major bothering you, firstly, make a plan to deal with it. If she asks you what's eating you, you can confide in your girlfriend, it's all about how you do it and what you do afterwards. Example :
I lost my job when I lived with my girl and my daughter was 1 years old. Imagine coming home and telling the little woman that. So I get a baby sitter, we go out for dinner and I tell her that I got canned. Whole department down the tubes. I told her how upset I was and how my manager sacrificed us to save himself and all of my frustration with that sh1thole. Then after I vented about my problem, I told her the plan. The plan would keep us going. The plan would get me back on track. The plan would work and I believed in the plan. And it did. We didn't have any problems during my year of unemployment, the bills got paid and eventually I found a new job.
That's how you share your problems with your woman.
What you don't do is get emo, get depressed, or despondent. Express, emote and then tell her the plan and follow through. You're human after all, you have problems and feelings , but your a man so you solve them and make it better.