hai im dr.hema physiotherapist. i understand your concern. yes its right time to join gym.you can continue for 3 months and once pregnancy is confirmed you can limit exercises to general body exercises for relaxation and walking can be continued. For 3 months physical activity and high fiber diet plays role in reducing weight. 1.Engage in physicial activities like Cycling, jogging, swimming walking for at least 30 min 5 times weekIy at gym. 2. Drink more glasses of water,when you are thirsty please do not take any other fluids as a substitute like juice, coke, etc . 3. Take green tea twice daily that burns fat and keep you active for 3 months. Eat lot of fruits and vegetables, this will not only reduce hunger but also add to the bulk of the food. once you stoped going gym......to maintain weight continue with stressless walking ie tolerable,yoga or meditations,eat fresh salads of fruits and veggies each snack,buttermilk 2-3times per day,eat normaly and avoid high fat foods. that helps to maintain weight and after pregnancy 1-2kg weight gain per month is expected after 3or4 months(physiological weight gain). i think my answer will help you to take decision. in doubt get back to us.all the best.