Doctor says its OK. Taking 40mg of atenolol, 0.5 mg of Klonopin, (clonazepam) and 50mg of sertraline all once a day. Is this OK? I'm afraid of drug interactions

Check it out. You can use a drug interaction checker whenever you have questions about drug-drug interactions or drug - food interactions. Here is 1 option (Drugs.Com): Your pharmacist is also a good source of info.
Should be fine. Those medications usually work fine together and the dosages are reasonable. If you experience any issues you should get in touch with your prescribing doctor! Stay safe! .