Took me 3 cycles to break 3. For starters I never ran a day in my life and started when I was 34. First cycle I averaged about 55-60 a week and ran a 3:0X. Second cycle wasn't that long maybe 8 - 10 weeks. Ran 3:0X again but 5 mins faster. Upped my mileage (80s) for a couple months during the summer and ran 2:5X that fall. Going into the 3rd cycle my PR in the half was only 1:27. That mileage gave me a monster boost. Mileage works. At least for me it did. Never broke 5 in the mile. Came close but never broke it. I'm naturally faster at the shorter races. Even in my late 30s I can drop a 24sec 200m. Like others said it may take a few cycles. Don't give up. Just be consistent