Should I let go of my current relationship or continue to make it work?

Aloha and thank you for sharing your question with us.  I can imagine this is a hard topic to think about and is probably quite stressful.  Opioids are truly uniquely challenging in many ways and very often, the person struggling with that challenge also has co-occurring conditions as well.  

There are certainly resources available to the person who needs support in this area. There are medication assisted treatment centers that exist almost exclusively to handle these type of condition with a combination of medication (hence the "medication assisted") to stabilize the withdrawal that is likely, and with counseling support to address the emotions and the likely co-occurring conditions with it. It is important that the counseling support is present.  The medication alone will not be enough to make everything okay again, but it is a good start and a portion of a complete treatment approach.

You mentioned having your own mental health concerns as well. Most people do have some items that need some work, so that is fair and please show some grace to yourself as you are at least able to acknowledge this, which is a step ahead of some who are not yet ready to seek help proactively. Some sources estimate that only about a third of people that need help actually reach out for it, sadly.

As far as your question to stay with your partner or not; that is a personal choice of course. However, what can help you make that choice is really honestly assessing the situation and comparing it to how it impacts your life. Although it may sound cliche, many find it helpful to make a pro/con list and think about it as objectively as possible. Some choose to consult a friend or family member.  In the end, it is your choice to make and I know it can be a hard one.

If you decided to stay and things are not healthy for you, at some point; you may consider why you'd like to stay in an unhealthy scenario. If you decide to take a break, it could be possibly to maybe reconnect later when the opioids are not an issue any longer and some work has been done so that your partner could offer their true selves without the influence of drugs.

It is truly a tough choice, but it is therapeutic for your autonomy to make it independently.  You can work with a therapist to help you sort out which items are important to you as you make your decision however and I would encourage you to consider that so you have an objective person to share your thoughts and feelings with as you navigate this challenge.   

I hope this helps at least a little and wish you the best of course.