Good to hear you’ve had good experiences with the POP so far. Are you getting any other irregular bleeding, e.g. after sex? Irregular bleeding can happen with the POP - we think that of women who’ve been on the POP for a year around 5/10 will have no bleeding or v infrequent, and around 4/10 will have a few episodes of spotting. So this might explain your symptoms.
There’s also a couple of other things to think about, which may or may not be relevant for you. If you’ve had a new sexual partner then it’s a always good idea to have a check-up for STIs. If this is the case you can search here for your nearest clinic https://sxt.org.uk/. The other thing is make sure you’re up to date with your smear tests - this is done every 3 years if the last one was normal, or more frequently if it wasn’t. If you are due a smear test this should be available at your GP.
Hope that’s helpful,