Hi sarah645,
As Novosbed mentioned … back issues are most commonly caused by comfort layers that are either too thick and soft originally or deeper support layers that are too soft for the person sleeping on the mattress (or layers that have become that way because of the use of lower density or quality materials). This allows the pelvic girdle to sink in too far and “tilts” the pelvis or bends the spine into a non neutral position which can cause the back ache…
A mattress that is too firm can also cause alignment and back issues but this is less common and I would think that “too soft” describes your situation better. Too firm is also easier to “fix” because you can add a topper but too soft means that the most effective solution would be to remove or exchange some of the layers and replace then with firmer or thinner ones which of course isn’t possible with most mattresses.
If your issue is that the mattress is too soft (which seems likely since the Prodigy is on the softer side) then post #4 here may provide some temporary or partial solutions which may help in the short term but the only long term solution would probably be a new mattress.
If you are looking at buying a new mattress … then the first place I would start is post #1 here which has the basic information, steps, and guidelines that can help you make good choices.
You are also in a good area because there are some good quality and value choices available to you in the San Francisco Bay area and the better options and possibilities I’m aware of are listed in post #2 here.
As you can read in post #2 here there are really only three ways to try to match another mattress which is by feel, by design specs, or by equivalence. It may be helpful if you knew what was in your boyfriend’s mattress which could at least give you a starting point but if you don’t then I would “rate” it by the criteria that are linked in this post and then use your more objective ratings for each of the different criteria to decide which mattress was either similar or better. This would give you a much less subjective way to choose a more suitable mattress that is a better fit for you in terms of PPP (Pressure relief, Posture and alignment, and Personal preferences).
Hope this helps.
Phoenix