Bac type cancer stage 1n lobectomy in may. no further treatment, ct now shows sm spot same side and fluid, i just know cancer is back, right?

May or may not be: It is not unusual to have some postop pleural fluid in the chest after lobectomy. So if it is a small amount, then you do not have to worry yet. But if the fluid collection is progressive or very large, then there is a higher probability that you may have a recurrence of your cancer. Your doctor can guide you for further monitoring or additional diagnostic tests to sort this out more clearly.

Not so fast!: Post op changes can be quite difficult to discern. Bac is quite slow in growth, but may be multifocal at the start (yours wasn't) or develop later. True bac is not invasive, but adenoca may have bac features, or start as bac. Ask if your tumor was tested for codon 19, 21 mutations. Check with a medical oncologist too. I doubt this is recurrence.