A.K. Maybe you can think of this in 2parts:
1- you are not obligated to be part of the wedding party. People refuse for all kinds of reasons-cost, time, prewedding obligations,etc. Even if you have agreed, you could still ask to bow out. If your friend knows you well, they may know about these stressors in your life. If you are already stressing this much, make the call tonight or tomorrow and take this burden out of your life.

2- After #1 is taken care of, reevaluate actually attending the wedding. You may be able to convince yourself to attend the wedding ceremony or the reception, both, or neither.

Don't attend just because it is an obligation. When wedding invites are sent, sometimes there is relief that some people have declined because of the ridiculous cost the bride and groom are spending on this one day event. Don't even get me started on that.

You can always send a small gift and card even it you do not attend. I hope you do what is best for YOU! Best wishes.