Try to get a nice rythm, maybe count with every breath. It helps me a lot if I count from 1-10 and start to again from 1.
And to your question with the thoughts:
Don't specifically meditate on it since that can be very stressful. Thoughts come and go as they want, just let them fly around you. If one comes to your head, meditate a bit on it and when you start losing yoir focus on your meditation, let the thought go and focus on your body, breathing and meditation again.
TL;DR: Focus on your breathing rythm and body rather than one thought alone and if one comes up, meditate on it until you start losing your focus on the meditation itself.
Hope I was able to answer your question 🙂