advice very much needed...?

So before I feel pregnant currently 5 weeks. I lost 3 stone went from 17stone to 14 half stone. Then then feel I have pcos and fibromyalgia and hyper mobility. So keeping my weight down has helped. I lost the weight by meal replacement shakes only. Trubble is Ive now put on weight currently 15st 3 my exercise is limited due to pain. I'm getting married next month and have worked had to get in my dress. This pregnancy means the world to me as it has taken 5 years. Do u think its will be OK to have shake and banana in the morning and healthy lunch ie fish and veg salad or fruit and shake for dinner. I'm worried I'm going to be putting all my weight back on Im getting married on the 8th August 2018 and already put on half a stone. Anyone keeped on a diet in pregnancy I'm going to seek advice from doctor but just wanted tips xxx