I think that it’s unlikely that you’re losing a fertilised egg each month. If this were the case, it would be unlikely to be such a regular occurrence, and it would also not explain the brown discharge and pain that you continue to have until your next period. I do think it would be a good idea to arrange to see your GP about your symptoms.
Firstly, it’s possible that you have some sort of infection that is causing the bleeding, and if this is the case it’s important that this is treated promptly. Secondly, an examination is necessary to ensure that your cervix is healthy and that there is no swelling or abnormality in your pelvis (a smear could also be taken if one is due or seems necessary depending upon the examination). If the examination and results are normal, then it would be reasonable to wait and see whether this problem settles over the coming months before considering a referral to a gynaecologist for further advice.