I have pain in my left breast for around 2
Seems to be related to hormones...
It's difficult to identify the exact cause without a physical examination. However since you reported lack of menstruation for 2 months, the breast pain may be related to hormones, the ones that are related to menstrual irregularity too. In my opinion, you should see a gynecologist to evaluate further.
Beside hormones, some times breast pain could be related to inflammation (mastitis) or other muscular or respiratory condition. Careful clinical and local examination is essential. You should consider visiting the gynecologist.
In the interim, start antiinflammatory drugs such as ibuprofen for pain relief. Warm compresses and evening primrose oil massage may benefit you.
Hope this helps. Let me know if you need clarifications.