Weight issue after birth.

So apologises this might be a long post. * not entirely sure this is the right group*

Quick background - I've always always always had issues with my body. Some days are worse than others to the point where I just don't want to eat. I have a history where I might have stopped eating for a day then the next I'd be okay again. Anyways I've never ever been happy no matter what but I need some advice. Honest opinions matter the most!

Below is a photo of me prior of any of my pregnancies. I'm 5'3 and according to my BMI I was classed as slightly over weight.

Below is another photo of me holding my son (who was 4 months old). Had no clue on my BMI as I refused to get on the scales.

Below is a photo of me now. I'm 12 weeks pregnant with my second baby (wasn't planned was going to diet and lose my weight before trying again)

I had my booking appointment and met with my doctor I was shocked to be told that I'm now classed as obese! So obviously with my prior issues of my weight has dishearted me even more. I guessed I'd be overweight because I was heavier then I was before but I never imagined I'd ever get to the stage where I was classed as obese. Anyways in shock of all the news (which I was told after having my scan so happy feelings to extreme sad feelings in the matter of minutes) my doctor explained how I will need to take higher dosage of folic acid and that I will need extra testing (which I never had to have in my previous pregnant) I just sat there in complete and utter shock, so upset couldn't even bring myself to talk.

Now my husband is so supportive but wouldn't say a bad thing to me. He doesn't believe in BMI as athletes can be classed as obese because muscle weighs higher than fat but as you can see I don't have much muscle at all!

Anyways I'm not sure whether I should really force myself into a strict diet and exercising routine (which I was going to do before I found out I was pregnant) or just take it easy, try accepting myself, eat healthy but relax.

Any opinions, views or advice would be greatly appreciated.