Move it out of the bathroom because humidity and temperature swings in there speed up alcohol evaporation and drain the potency - that's the main thing. Perfume should be stored somewhere cool, dark, and dry, ideally in a closet or drawer. If you leave it in the bathroom for three months, it's normal for it to lose strength pretty fast, but once you move it somewhere else it should last longer on your skin, like a solid 4-5 hours. Also check if it's eau de cologne or eau de toilette because those formats have less fragrance concentration than eau de parfum, so they naturally don't last as long.