Launcher not launching

Hey Mojang! So I started playing Minecraft and it was amazing! Btw, I downloaded the java edition for my Windows 10 pc. I downloaded a few mods, made a world, and it was perfect! About a week later, I pressed play on the Minecraft home screen. It loaded by saying 'preparing' as always, and it loaded all the way. Then it just sat there for a little while so I pressed play again and it said 'game already running'. So I hit 'start anyways' but nothing happened. It keeps doing this over and over and I haven't been able to play since. I really hope you can help me fix it! Thanks so much! (: