Is my dog in actual heat or is this a pre heat stage?

My Lab is almost 11 months old. She is a little more ignorant that usual and every male dog we met yesterday wanted to hump her but there are no other signs of heat. Is this heat? Is she fertile? Is it time to isolate her already?

I don't want to isolate her too soon and have her going without her freedom for longer than needed. She's very big and very strong so walking her on a lead whilst she is in full heat would probably not be a good idea as she could get away from me if she really wanted too. She's not been spayed as we are planning to have one litter when she is old enough - we already have potential homes for any pups.