Can Doctor's tell by if a lump is a cyst from an examination?

I found a lump at the top of my left breast about 4 weeks ago. I had an examination a couple of weeks ago and the doctor said it feels like a cyst and not to worry. She asked if I had any family history of breast cancer, which I don't, and she said to only go back if the lump grows or anything changes. The lump doesn't seem to have changed but I think I can feel a further lump not too far away from the first. I am planning on booking another appointment to have this checked. I wondered if anyone could advise whether I should push for a scan or not or whether cysts are easily identifiable by GPs from an examination. Also is there any particular type of scan that is best- a mammogram or an ultrasound?
I'm 34 and otherwise heathy and the lump isn't painful and is about the size of a pea.
Any advice is greatly appreciated xx

I've never had a mammogram I live in the uk and unless you have a family history of breast cancer they don't start routine screening until you're 50.

I'll book another appointment with my GP. Thanks for your response x