PMS OR PREGNANCY SYMPTOMS??!

So I’ve had my IUD Lyletta for about a year now, there have been no problems with it. I can’t check the strings because they’ve curled up & my gynecologist said that was normal & if I ever needed them checked to just go see her. So anyways my period is pretty irregular but ever since being on the IUD it’s been starting to regulate.

So my phone has been deleting apps & it deleted eve so I lost all of my past period dates & had to start over. I wasn’t sure how long my cycle was. My last period was very light so I was only bleeding or spotting for 7 days. Now my “predicted” period is 2 days late.

I’m worried because I’ve been experiencing pms symptoms- mood swings, light cramps, nausea, & fatigue. But something new has happened. When I get pms my boobs don’t swell but now they’re starting to swell & feel sore. I have very small boobs so it’s something me & my boyfriend noticed. Idk am I overreacting, is my app predicting my period too soon, did i enter the wrong days for my cycle?

I know the IUD is 99.9% effective but how often is the IUD a failed contraception?

& when should I take a pregnancy test?