I wouldn't be so quick to doubt yourself. BJJ can be for everyone regardless of physical ability. It was developed specifically so a smaller and weaker opponent could not only survive an attack but come out on top. Grand Master Helio Gracie was well into his 90s, could barely do a pull-up, and was still tapping guys out half his age and twice his size. Finding the right school that can work with you is important though. Some places emphasize competition and may not have a welcoming environment for people who don't want to compete. Try to find an academy that focuses on self-defense and I'm willing to bet they'll be very accommodating. It's a great activity for kids to get into too!