TTC exercising more and late period

Recently I’ve been exercising more to lose a bit of weight to help fall pregnant. We’ve been TTC for a while now and I was hoping this might help as I read good things about it. However my period is a couple of days late and it is never late, I’m very regular. I took a test a few days ago and it was negative. The only period symptom I have are very slightly tender breasts. But not as much as usual before a period. If exercising more has messed up my cycle, how can I get it back on track to keep TTC? Has anyone experienced the same problem?