I hear you. You're busy taking care of others and you can't find enough time for yourself. Maybe try to set some boundaries to give yourself some time for your own enjoyment, whether that be looking for sex or just anything else you enjoy.
Grindr is not really good for anything except random hookups, as you've found. You might try dating apps like OkCupid, Hinge, or Bumble if you're looking for a more meaningful relationship. You might want to consider what you're looking for, though. You say you "need some actual sex to relieve some tension". Think about what you mean by that: random sex, but not like what you've been getting, or a more meaningful connection with a person. If you were to advertise what you want, say on Grindr or a dating app, what would it be? "Bi boy seeking actual sex to relieve tension"? Don't get me wrong, I'm not judging, and I've had a lot of random sex just for fun. I'm just suggesting you think about what you're looking for.
Random hookups via Grindr or similar can be okay, if you make sure you're on the same page with a potential hookup, in terms of boundaries and expectations, before you meet. Set your boundaries and make them clear. Get positive agreement. If he's not willing to agree or wants more or something else, don't go through with it. Trust your gut instinct. If the other guy seems pushy, dismisses your boundaries, or gets angry when you say no, that’s a red flag. It’s better to walk away than put yourself in a situation where you feel pressured or unsafe.
Girls are an entirely different story, as you might have guessed. You won't find too many girls on apps looking for random sex. This is where it would be a good idea for you to consider what you want - sex to relieve tension, or a relationship. I've never used apps to find girls so I can't speak from experience there, but you might want to consider ways you can meet girls in real life, and that doesn't have to be in some seedy bar. Join community groups, or a club if you have a hobby. Get involved, make friends. The more people you know, the wider your field of potential partners. If nothing else, if you're out and about in that free time you have (because you set some boundaries), you're taking your mind off yourself. It would help to try to stop thinking about getting sex and more about how to enjoy yourself and connect with people.