Sertraline is a SSRI - Selective serotonin re-uptake inhibitor, having a very commonly observed side effect of gastric irritation, commonly referred as acidity.
Firstly few people can tolerate a direct dose of 100mg, but majority of the patients complain of gastrointestinal issues, so it should be introduced at lower doses like 25 mg or 50 mg, once tolerated should be gradually increased,
Next Steps
Considering other molecules available which are proven to be little more efficacious than Sertaline in case of OCD with lesser side effects like drowsiness and sleep disturbances (again a observed side effect of SSRI if given at night may hamper sleep architecture for some patients), a shift to another molecule can be suggested.
Health Tips
If there is response to Sertraline, then side effects should be tackled with Antacid like Pantoprazole/esmoprazole, or consider taking dose of Sertraline in between ur meal (take half of ur routine meal, consume the tablet and then finish the rest half of your meal), if still unbearable side effects consult a psychiatrist to reintroduce the drug with the policy of start low dose go slow to increase the dose.