They can absolutely tell this early. My ectopic was identified via bloodwork (very low, barely doubling betas), then confirmed via ultrasound at 6 weeks. Pregnancy was a result of FET, so my dates were exact.
If you are 7 weeks, and a trans vaginal ultrasound shows an empty uterus, then that’s plenty of confirmation for ectopic. Don’t delay on this.

It's not too early for an ectopic. I had one at 7.5 weeks. Your doc should know if it's increasing appropriately. There is a standard general approach. If you don't trust it don't mess around tho

I've been feeling some pressure/
discomfort on my lower left pelvic area and wondering if this is normal in early pregnancy or if it could be a sign of ectopic.

I'm concerned because my betas are rising slowly but not doubling, last one was 750. I asked my doc about possibility of ectopic but they said they can't tell this early and I haven't had any bleeding to indicate that.

I'm around 7 weeks since my last menstrual cycle, although my cycles are irregular and sometimes ovulate up to two weeks late.