You're still within the average time frame so I wouldn't panic yet. Do you know the types of fish you have in the tank? A 38 gal is a large tank so if the fish are very small and not giving out enough of a bioload I think it's possible the cycling process will be extended but I'm not 100% sure on that. Also what temperature is your tank set on?
Here's what I would do if I were you:
1). Stop using the Tropical Science stuff. Obviously it isn't working anyway and even though the description says it contains the "correct" bacteria we don't know for sure and it's possible that the bacteria it does contain is the wrong type and is stopping the correct bacteria from forming.
2) Add Prime BEFORE the water goes into the tank. If you add it immediately afterwards and the filters are off it may not be an issue but Prime should be added before the new water goes in so that the chemicals are neutralized properly; if they aren't it can kill off the bacteria you need in the tank. So either add Prime to the buckets before you add it back in or add Prime to the tank first (add a full dose for the volume of the tank though not just the water you are replacing if you do it this way) and then add the new water in.
3) Try to get some seeded media. It always helps regardless of where you are in cycling. If you can't get any near you,
Angels Plus sells "active" filters from their fish tanks and they've helped many on here -- myself included -- with their cycles. Just make sure you get one that says "active" next to it or else you're just buying a plain filter.
Let's try those things and see what happens. On average it takes a couple of weeks for ammonia to drop to 0 and nitrite to follow but every tank is different and it can take up to 3 months for the full process so try the steps above, keep testing and doing pwc as you've been doing, and let's see what happens in the next couple of weeks. Just FYI it took me 7 months total to fishless cycle a tank for whatever unknown reasons so I feel your pain. Mine is a long story so I won't go into it here but it goes to show every tank is different because of varying factors (water source, etc) but the good news is it should cycle eventually and it shouldn't take nearly as long as mine did.