We are actually going through as bit of a rough patch anyway, and need to sort a few things out before I can concentrate on the bedroom stuff
This is key. IME. Women and men tend to experience sex drive differently and one thing which is huge for most women (NB; it isn't exactly split down gendered lines; this is a simplification, but it does work for most) is feeling safe and secure. If you don't feel safe and secure within the relationship the desire for sex just won't be there. And unfortunately any kind of pressure for sex is actually counterproductive. You can't improve a marriage by throwing sex at it. Sex is kind of like a barometer, really. How good it is and how much you're enjoying it and how much you want it is all related to how you feel about the relationship in general and how much you've got going on in your lives.
Do you feel supported by your DH? If you don't feel supported you're likely to either be overstretched which leads to a lowered sex drive, or feel resentful, which makes you less likely to want to be intimate (not just sexually) with him.
Do you feel like an equal? If you don't then it can be the case that sex (subconsciously) starts to feel overbearing, not in a good way.
Do you enjoy it when you get into it or do you also not find it that great unless you've initiated? It can be a huge problem when sex becomes a chore, it kills your ability to find the fun and excitement in it.
You seem to be very focused on frequency where IME this is not really relevant. In marriages with a healthy sexual relationship there is ebb and flow and often a pattern where some weeks/months sex will be every day or every couple of days and sometimes weeks without any sex at all and this is a fairly normal pattern, similar to any other activity you might do for fun. Sometimes you have the mental space and the desire for it and at other times it doesn't really appeal to you as much. Most things we do would become boring if we decided that we had to do it at least once a week no matter what.
BTW, many "trivial seeming" troubles can be how we tend to experience an unequal marriage or one where emotional abuse is present. It might be worth exploring (privately) if you think this might be the case. Certainly before you try "more sex" as a solution, but better communication and just general caring for each other tends to lead to a better marriage and by extension, better/more sex.