In short, yes! Absolutely you should have your say in any relationship. But a common challenge of being in a romantic relationship with someone older is that they may have more say than you in making decisions, and you might feel less able to be honest with them about how you feel.
You may think you are ready to be with someone older, but their expectations about sex and other things could be very different from yours. Remember, it is always your right to say no to sex if you want to. And if you are being forced to be in a relationship, or even marry, someone older, this is not okay. You do not have to give your sexual consent to anyone, you always have the right to say no to sex and marriage.