The symptoms you describe, giddiness, nausea, vomiting, a cold sensation, and acidity, can occur as side effects of both Newven OD and Krimson 35, and taking them together is generally considered safe if prescribed by your doctor, though side effects may feel more noticeable initially. Weight gain is not very common with Newven OD, but Krimson 35 can sometimes lead to mild weight changes due to fluid retention or hormonal effects. To reduce symptoms, take medicines after food, stay well hydrated, avoid skipping doses, and give your body some time to adjust; however, if vomiting is frequent, symptoms are severe, or not improving after a few days, you should consult your doctor to review the doses or consider alternatives.