I get quite a few days with EWCM, so a different story - still hard to predict ov from it though, as I never know quite how many days I will get (varies a lot).
It is possible if you don't have much FM to have a short fertile window as the sperm need the FM to survive for any length of time.
Is the problem that you can't predict when you ovulate, or that you can only predict it to within a couple of days? If the latter, maybe Pre-seed is your answer to help the sperm survive a little longer...
Grappa some women do not have a lot of fertile mucus, some don't have any at all. There are a lot of urban myths of things you can take to increase your mucus (and therefore extend your fertile period) but I don't think any of them is actually proven to work. I think the best advice is to drink plenty of water as this will increase the amount of mucus for you. Sounds simple, I know!
Have you tried charting/temping? This will show you when you have ovulated by showing a clear sustained increase in body temperature. Done over a few months you will clearly see when ovulation has occured, rather than the OPK kits which just show you that ovulation is about to take place.
The egg only lives 24-48 hours, so the purpose of the fertile mucus is to nourish the sperm until the egg is ready to be fertilised. This is how women get pregnant even if they have sex three, four or even five-six days before ovulation, it's because they have had enough mucus present to keep the sperm alive until the egg is released. So it may well be that your fertile period is shorter and restricted to the time of ovulation if there is scant fertile mucus. Assuming no underlying issues with sperm quality/quantity I think it would be good advice to have sex more than once per day when you know you are about to ovulate.
If you don't have a lot or any fertile mucus try as much as possible to 'time' your intercourse as close to ovulation as you can. I'm sure it will happen for you as you have already done it once!! Fingers crossed for you!