One thing you shouldn’t feel weird about is needing a mattress topper to fine-tune your sleep comfort. Just like you’re noticing with your new Black Oasis mattress, sometimes a little extra help, especially for your shoulders, can make a big difference. Frankly, there’s no guarantee that switching to another mattress would fix the issue… or not cause a new one.
When people have discomfort like yours, it’s often the pillow height (or “loft”) that’s actually the main issue.Broad shoulders and not enough loft is often a recipe for shoulder discomfort when sleeping.
Toppers are a great way to adjust comfort indepently or with the correct pillow/s when only one of them alone aren’t cutting it. In fact, many super high-end mattresses (even the $10k+ ones) are designed to work with specific toppers for this reason. I would not underestimate the value of the topper. It is easy to dismiss it’s value, but it is worth adding it to the sleep system. I suggest working to see if a better aligned and structured pillow will make a meaningful fix.
Hopefully, you’re using a new foundation or one that matches up with your Black Oasis. If the slats underneath are too far apart, that can cause problems. I would guess the Black Oasis is meant to be paired with a semiflex foundation. An old foundation may have some flexing in areas that can affect the support of any new mattress placed on it. Therefore, using a previous foundation, may be a bit of an unknown risk.
Also, since your mattress has a pillowtop, expect it to soften a bit over the first few months. That said, it’s still a good idea to keep looking for a pillow that gives the right height and support, especially for side sleepers with broader shoulders.
Hopefully, this offers some insight and options.
All the best,
Maverick