Hello and welcome to the forum. Thanks for your question. It's pretty common to worry about our health and having breast cancer when you are a woman is also quite common. Do you do monthly breast checks? This is recommended and here is a link on how to do it: https://www.mayoclinic.org/tests-procedures/breast-exam/about/pac-20393237 If you do this around the same time each month, it gives you a good picture of what is going on with your breasts. Try to avoid the time during menstruation or immediately after as there can be temporary breast changes during that time.
Age is a factor. The younger you are, the less risk you have. You do not appear to have any family history. Stay healthy to help prevent breast cancer. This means maintaining a healthy weight, regular physical activity, eating a healthy diet, getting rest, not smoking, limit alcohol consumption, etc.
As to your concerns, it never hurts to get checked by your doctor. Hormonal fluctuations can cause breast tenderness and pain. Using the muscles in that area in a way they aren't used to can also cause pain you don't expect. I will tell you that I had to investigate something I realized it was from playing tug o war with my dog and using my chest muscles when doing it! It can be that easy to strain those muscles (or maybe that is just me. :)) If you have a lump, yes, get it checked. But having a cyst is not uncommon either.
Do you have anxiety in general though where you worry a good deal? That in itself is something that people often benefit from addressing. https://www.psychologytoday.com/us/blog/fighting-fear/201305/the-treatment-health-anxiety
Hi there. Hey, this is a particularly stressful time for us all. When we are stressed, it makes us worry more. We think about death and our mortality. Could this be going on behind the scenes with you? You are not in a high risk category from what you have said. Live as healthily as you can and that is all anyone can do. If the stress becomes too much, then work on anxiety. A therapist can be a wonderful thing. :>) hugs