All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is obvious that you are overwhelmed by OCD and Waswaas (obsessive whisperings). What you should do is perform Ghusl upon seeing one of the two signs of the end of menses: the white discharge or dryness (i.e. the cessation of blood). You should disregard any brownish or yellowish discharges that you see after that, as yellowish and brownish discharges after the end of menses are not considered part of menses according to the preponderant opinion of the scholars.
Hence, you attained purity the first time your menses was over and you performed Ghusl. The yellowish discharge that you saw after that is not considered menses. If you do that and perform Ghusl upon seeing the sign of purity, you will not be confused at all. If it is difficult for you to determine purity or distinguish the yellowish discharge from normal wetness, and given the fact that you suffer from OCD, you may follow the scholarly view that the brownish and yellowish discharges are never considered part of menses. This was the chosen view of Shaykh Al-Islam Ibn Taymiyyah . So whenever the red blood ceases, perform Ghusl and pray.
As for the ejaculation, we believe that this is generated by your doubts and that it is not actually ejaculation. In any case, you are not obliged to perform Ghusl unless you are certain that you ejaculated to such an extent that you can swear that you did. Without such certainty, you are not obliged to perform Ghusl. If you doubt whether the discharge is ejaculate or something else, you may choose what to consider it to be and apply the relevant ruling.
Finally, you should strive to ward off obsessive doubts and give them no attention whatsoever for, indeed, getting carried away with them would lead you to grave evils.
Allah knows best.