Ah yes, overthinking is not a fun thing to do. And especially when love relationships are involved oh my... If in case you'd like to get rid of it, you can try praying the rosary everyday. It can give you peace of mind or perhaps whichever God deems you need at the moment.

If all else fails, we can pray and offer up our suffering (emotional, mental, physical, etc.) to God (with the intention of the relief of souls in purgatory, conversion of sinners, reparation of blasphemies against the Immaculate Heart of Mary, etc.) and He can lighten our burdens.

I gave my agonizing thoughts and heartaches to the Lord more than a decade ago (even without adding any intentions) and He truly did as He promised!!! I never thought it would do anything but the persistent pain was suddenly gone that I didn't even notice when. Glory to God in the highest!