Mazal tov on your recent wedding!
Based on what you write, your cycle is in the general range of forty-three days. In that case, you do have a rule of thumb of when to expect your period. Halachically, you should observe vesatot only on your interval day, unless or until your cycles shorten to thirty-one days or less.
If you are worried about the possibility of discovering bleeding at the time of relations, you are permitted (not required) to check first. You can wipe externally with toilet paper — not after urinating, or waiting at least a few seconds (ideally, about fifteen seconds) after urinating. If you don’t find staining, you can go ahead with relations. If you do find staining on the paper, you are not niddah but we recommend abstaining until about a day after it subsides, so you can clarify whether it seems like you are getting a period.
You may also find it helpful to explore fertility awareness. We discuss some of its principles here on our site regarding contraception, but it can also help with conception, and with being more aware of one’s body.
Although longer cycles are fairly common, cycles of this length should be checked out with a gynecologist. A gynecologist can employ a range of tools such as a detailed medical history, ultrasound, internal exam, and blood tests to get an initial sense of why your cycles are long. In the meanwhile, if you can optimize your diet and lifestyle for healthier eating and more exercise, these steps can also affect cycle regularity.
We hope this helps. Please write back with any further questions.
This response has been updated to reflect the rulings of our current Rabbinic Supervisor, Rav Kenneth Auman, regarding waiting before wiping.