I wrote something on a similar topic, masturbation, and the instructions in there will also apply to you:
Which action is more serious – patronizing massage parlors or masturbation?
On top of that, for the two of you, your occasion of sin is being in a private enclosed space. This is your occasion of sin, meaning that when the two of you are in an enclosed private space, your tendency to fall into lust is very high and that you do not have the strength to fight it. You must therefore help one another to commit to never to enter in an enclosed private space. Plan all your activities in a public space. And if you were to travel together, invite others to travel along never spend a night in the same room. Your history proved that you did not have the resolve to resist the temptation. Then avoid it.
Prayer however remains your main program. Since both of you are Catholics, every time you meet, pray first. Specifically in your prayer to ask God to keep you both pure and to be there not to tempt one another, but to protect one another from falling. Lust is the opposite of love: it objectifies and demeans the other; it uses the other to gratify and it reduces the other to the merely physical level. In the long run, frequent fall to lust short circuited the space for deeper listening and understanding, depriving and disabling your ability to know and receive the person as you become too used to stopping with merely the bodies. That’s not love. That’s usage, both using the other and using yourself. The person is degraded.
Lastly, check out Christopher West. He is the well-known teacher and popularizer of the Theology of the Body. It is not hard to find his material online. I also highly recommend you to read his book: “Good News About Sex and Marriage”. There is a whole chapter in there addressing your situation. It is in a Q&A format and is very easy to read. It will revolutionize your life and your relationship. If possible, read it together.