How would I know if God were calling me to be a Jesuit?

There is no short answer to that question but if you do have the sense that this is a possibility for you, then you owe it to yourself at least to take that feeling seriously and make some enquiries.

There is nothing to be lost in asking questions or in finding out more about a particular way of life.

The process of discernment is about spending time checking out as far as possible the external or observable aspects of your feeling that God is calling you to this way of life.  This would include spending regular time in prayer, looking at what God is saying to you - perhaps through the Gospels, or through other scriptures.