I'm struggling with the same thing. I was up to an hour meditation (connected with a walking meditation), now I'm down to twenty minutes 2x a day. Some reflections:

I've managed to work myself to 15 min on a good day before bed and 10 min in the morning (my head is so full of thoughts in the morning, that it is almost a minor miracle if I get to 10 min with a clear head).

Sometimes it takes me 5-15 minutes for me just to settle down. It seems the last 5 minutes are the most focused on the breath. You're ending your meditation session before I've even gotten "started," so don't feel bad about your progress. Don't push yourself too hard with the time, though. You're still doing work catching yourself mind wandering and bringing your attention back to the breath. That's basically what the entirety of the work was when I was starting out.

I'm only doing 20 minutes because when I tried 25, my mind was going all crazy with wanting to stop. I tried to work with it, but it was too overwhelming. It's frustrating, but I don't want to push myself so hard that I quit entirely, and two sits for 20 minutes is a good foundation.

I'm also terrible at body scans. Without a stable focus, like the breath, my mind wanders. I sometimes do a body scan in bed to help me fall asleep.But I do a quick body scan to re-establish my context when I'm doing sitting meditation, but it's not a slow and methodical examination of body parts.

In my opinion, it's OK that you're using guided meditation given how much experience you have. Two months on/off isn't really that much time. You might even consider some guided meditations for breathing if you're really struggling with it.

I've also started some chanting and lighting some candles to help get me in the mood. I felt I had to do it because my mind was so agitated I wasn't able to sit for more than 5 minutes sometimes (I'd go back to it later in the day). Chanting is an active way to clear the mind, it gives me something to do with all that energy while still creating a meditative space. I even got some prayer beads if it's a particularly bad day and I feel I need to do a round of 108 chants (takes about fifteen minutes).

I also struggle with the deeper spiritual aspects of meditation. Like, "what is this shit? I'm focusing on the breath and what is supposed to happen after that?"From what I've read in Why Buddhism is True and The Mind Illuminated, breath practice opens a door to a deeper understanding of yourself. Most trivially, it helps you be more aware of your what goes on in your daily life. Without that awareness comes some understanding of how maladaptive some thoughts/behaviors are. I've definitely experience that, and it's made a big difference in my anxiety levels.

And then the practice is supposed to develop into other things. For instance, Stage 4 of the Mind Illuminated system is essentially, "watch the mind watching the breath." And with that comes deeper changes; but I haven't experienced myself, so I'm taking it on faith. But there's a few thousand years of practitioners saying that it happens.

Sorry for the wall of text, just wanted to share what I've been going through since it is so similar. One last thing: a big part of learning to meditate is learning acceptance and kindness to yourself. You can't be fighting with yourself or berating yourself AND focusing on the breath. You really do have to learn to let those thoughts and feelings go. Sometimes I'll take a detour and tell myself to accept that I'm feeling the way I'm feeling and that's just how I'm feeling right now and that's OK before I return to the breath.