Okay so in the manga (not sure if it was a one-shot or not) there were these two high school boys. Boy A finally builds up the confidence to confess his love to Boy B but once he does, a stray baseball or something hits one of them and they both end up in the infirmary. Boy B forgets about the recent love confession.

After this I'm not sure if the boys switch bodies to where their minds are in the opposite body or not but in the end Boy A tries to confess again and the same thing ends up happening, only now that Boy B remembers the love confession.

I'm pretty sure there was a body-swap because during the second love confession, the one that got hit by the object was injured differently after they woke up again.

The boys were injured where one was hit at the back of the head and accidentally head butted the one in front.

Sorry if it makes little sense but I KNOW that this manga is out there and I REALLY NEED to find it. 😢

The story Watashi-tachi ha byplayer from Joshi BL fits with the head smack scene but it was basketball not baseball and the rest doesn't match so it probably isn't.
There was a similar baseball scene in Konna hazu ja nakatta no ni. but the rest is compete try different.
Im sorry I'm not helping much but if it could help, try the "amnesia" or "body swap" tags in the advanced search.