If i lose a lot of excess weight, will i be more fertile and able to have a baby ?

Depends how much: It depends on how much excess weight you have to start with , and whether or not you have polycystic ovarian syndrome (pcos). In pcos women losing weight improves Insulin sensitivity and can decrease the risk of diabetes, may help with abnormal cholesterol, and can make menstrual cycles and ovulation more regular. In overweight women planning ivf weight loss may improve embryo implantation rates.

Yes: Obese women have greater difficulty ovulating, having an adequate endometrium, sustaining a pregnancy and having a healthy pregnancy. Therefore chances are that by normalizing your weight, the outcome will be improved.