Hi and welcome
As I'm unagented I can't answer your question, just empathise. There are lots of agented people here who will be able to tell you more. But really well done on getting an agent for your first novel - that's fabulous. It's a rollercoaster ride, isn't it? But one thing that agents and publishers do like is a second book in the wings, so if you can just shut your ears to the worries and plough on with it, it would probably be good. Especially as I see from your profile that your first only took you three months. You could maybe make a schedule and by autumn you'll have your second. Which your agent will either be able to sell to the same publisher in a two-book deal, or may even be the one the publishers will go for first!
Susiex