I apologize in advance if the beginning of this post seems to trail into more general relationship/sex stuff but I want to make sure I'm providing as much detail as possible in order to get the best advice for my specific situation.

TL;DR How can I tell my gf that i want her to dominate me without overwhelming her. And what are some ideas for things I can suggest we do now which can then be ramped up to become more extreme in the future ?

My gf (25F) and I (25M) have been together for 8 years. Over the past 2ish years our sex life has really taken a major hit where we aren't having sex very often at all (twice/month at most) and when we do it is very predictable, repetitive, & stale. Some of this is due to factors outside of our control but a big part is my GF having developed a lot of self confidence issues about her body. I truly believe these issues are a symptom of each other (we started having sex less due to some external factors which caused her to feel less sexy/desirable which then in turn caused us to have sex even less frequently and so on). Recently we've had a few serious conversations where I've expressed that I'm not happy with our sex life and feel like we've regressed from where we have been in the past. These conversations went very well and we both agreed to try and bring more excitement to our sex life.

I would consider myself a switch and I definitely have way more experience exploring my dominant side. However, I do feel I'm naturally more submissive and really want to explore that side of myself more. In the past on rare occasions I shared a bit of my submissive nature with my gf which resulted in us trying things such as playful SPH, ass worship, foot worship, locking me in chastity for very short periods of time while teasing me/feeding me my pre-cum, and fucking her with a dildo in order to simulate a cuckold scenario. This type of play didn't happen very often (even when we were having sex more frequently) primarily due to me being self conscious towards that side of myself.

With our recent decision to find new ways to spice up our sex life, as well as me becoming more comfortable being submissive I really want to explore my submissive side again with my girlfriend. and potentially ramp up to more extreme experiences. I would love to experiment with her locking me in chastity for a prolonged period of time (a month maybe) as well as possibly cucking me to name a few. To be clear im not expecting these extreme experiences to happen anytime soon (I would be fine if it took us years to work up to something like cucking or even possiblynnever doingbit if it isn't something my gf is willing to do). However, I want to begin submitting to her much more frequently as well as ramping up my submissiveness over time. I want to try and introduce this to her but don't know how to do it in a way that would be approachable for her.

Ever since I initially shared my submissive side with my gf, a few years ago, every now and then she'll make jokes about me submitting to her in different ways. Sometimes it's obvious that she does it just because she's horny and knows it will turn me on too. Sometimes she does it for no apparent reason. Either way these jokes are are pretty infrequent and harmless. In the past I've usually been embarrassed when she does it due to being embarrassed of that part of myself. However I'm beginning to become more comfortable with being submissive so a couple days ago when she jokingly said "so when are you gonna let me peg you" I told her sincerely she could this week if she really wanted to. I don't think she was expecting me to say that because she backtracked immediately.