parasites are always a possibility, and cleansing will not hurt anything at all even if you don't have them.
I looked up the product you are taking. The ingredients seem ok, if anything to start with. The problem is the dosage. I would start with 1 2x daily first day to see how you react. Day two 2 - 2x daily, then increase to 3-4 2x daily or 2/2/3 at 8 hr intervals to spread evenly. Its best to take herbs on an empty stomach, and if before meals atleast an hour.
The amount in each capsule is 500 mg. You need atleast 2000 daily, and that is a minimum in my opinion, but still it's good to start out slow and work up to optimum dosage based on how you feel. I'm sure you have been reading, if you start to get die off, then you know you are at a good dose to start. You will feel worse before better :). There is always the possiblity of candida, with long term Antibiotic usage. Raw garlic can help with both, and has amazing benefits to restore health.
Yes, bowel cleansing is important. I suggest at the minimum use psyllium once or twice daily, or there are packaged cleanses like Dr. Schultz and Dr. Christopher's products. I have taken both and both work well. I just buy psyllium at the drug store, it works good for me. Also enema's and/or colonics can be very helpful, as parasite cleansing can stop you up.
These are just suggestions based on my unfortunate experience. Everyone responds differently. Good Luck to you!