Why am I not getting faster?

This thread is more of a frustrated vent than a request for advice, but input is appreciated. I am talking fly. When I first got back into swimming (about 6 months), I timed myself for 25s. I went 15/16 from a push, but I could only do it twice before I died. After a few weeks, I could hit 14/15 for 2 or three. I continue to do timed 25s on my sprint day so that I can measure my progress. I have hit 13. Last practice, I swam 14/15 for 8 25s. I have also added a 25 slow freestyle in between and now I do them on 1:30, which is just enough rest to feel fresh on each. It sure feels like I am a lot better, but If I am not faster, am I really? I am sure I'm a lot faster for a 50 or 100 (ie I can now survive 100) due to endurance, but shouldn't I be faster too? It doesn't seem to make a difference how fast I turn it over, either. If I am swimming hard, I swim 15. Breaststroke is actually opposite. I can build those (actually, just by going all out, I build) as I am around 18 for the first couple and 16 by the 8th. I have improved 6 seconds in my breaststroke 25 since I started. Total yardage is about 2000 3 times a week, which is all the time I can afford to get to the pool these days. Maybe I am getting impatient. I'd call it a plateau, but there was really no progress before it flattened out. :rantonoff: