Hidden twin??

Tiffany 34, 💛💚💛🌈👼🏻 💖💜

Anyone else have experience with a hidden twin showing up after the first trimester?? My last ultrasound was at 11 weeks showing one baby, but I SWEAR the last few days I’m hearing 2 heartbeats on my home Doppler... and no it’s not mine. It sounds like 2 super fast heartbeats over lapping one another and getting more prominent each day. I’m 13 weeks 4 days now. 😳😳 what is going on here?!?!