The age of consent is 16, save for certain situations where a person in a position of trust cannot have sex with a person under the age of 18. A classic example of that is teachers. So save for that relatively unusual exception, you are past the age of consent. So you can have sex with whoever you want. No, you certainly don't need a boyfriend to have sex. It's up to you how and with whom you have sex. Just make sure you are comfortable with everything that you do; remember that it is absolutely your right to say no to something at any stage, even when you've already started being intimate or having sex with someone.
Two other quick points to note. First, keep yourself safe, both in terms of the physical situations you're putting yourself in and practising safe sex. Sex is inherently a situation where you are going to be vulnerable with another person or people. You obviously cannot guarantee that people are going to treat you the right way or make good decisions, and there will absolutely be times when you have bad sex, or do something you regret. That's fine. It's all part of the learning process. But you should take steps to keep yourself safe in terms of things that you can put in place and steps you can take in advance of becoming involved with someone.
Second, this is a process, both in terms of learning how sex works, and learning what works for you. Having a good, satisfying, happy sex life includes constantly learning new things both about yourself and the person/people you're having sex with. It's not all going to be smooth sailing, even in a long term relationship (and perhaps particularly in a long term relationship). There'll be times, as I say, when you do things you regret, you do things you don't enjoy and so on. There's nothing wrong with feeling bad about that, but ultimately you should see it all as part of the process of figuring out what you enjoy. So do keep an open mind, and don't be put off or think there's something wrong if you have bad experiences, particularly early on.