Welcome to HCM,
You have Gestational hypertension
and swelling in lower limbs, this is good that you are not passing Albumin in urine which is Pre Eclampsia
This is normal to gain in weight up to 10 Kg in pregnancy
,you should take care of diet that it is not deficient in nutrients yes you must take salt in less quantity as B.P. is high.
Your groin pain during walking may be due to muscular pain
or joint pain in the hip as ligaments get lax in late stages of pregnancy.
Your swelling may be partly due to pregnancy itself and Nicardia can also cause swelling in limbs so please consult your doctor and discuss if it is possible to change the medicine like Labetalol
Weight gain is mostly due to less physical activity and more calories consumed but you should take care first that you successfully complete your pregnancy then after words you can lose weight and regain your health.