Bit o' science time....

In order to get AF you need bodyfat. This is because your ovaries and pituatry gland make estrogen but it's metabolised quite quickly unless it has been absorbed by fat cells. Thus if you don't have enough fat (a BMI under 20) you don't have periods.

Fat cells also MAKE a small amount of estrogen, which is why obese men can develop gynacomastia (grow breasts) and why PCOS both causes and is made worse by obesity.

So, to your own situation, for many years your body has become used to a larger amount of estrogen because it has been stored in your fat cells. As you lose weight your hormone levels will adjust. For many women this is a time when absent AF returns or heavy AF becomes lighter. For some there is spotting or cycles getting longer/shorter. Your body will get used to your new weight and normalise over time.

Keep an eye on it, and if at any point YOU feel there is something wrong then go see your GP who can make sure you aren't PG and do some bloods to check all your levels are ok. If you didn't ovulate this month there's a chance you have very little lining (it builds in anticipation of ovulation) and have little to shed in a period.

Really don't worry about the TTC - studies have shown again and again that the most positive things a woman can do to fall PG is be a healthy weight and not smoke or drink to excess.

Best of luck

Bec