My most recent haflaga was 35 days. Before that, I had a haflaga of 28 days for at least 5 times in a row. However in Elul I got it at night whereas in Tishrei, Cheshvon, and Kisleiv, I got it by day. Therefore I am assuming that I did NOT establish a regular pattern. I am therefore assuming that I do not need to keep 28 as a calendar day this month because my last haflaga was 35, as previously mentioned. Let me know if this is correct.
You did establish a pattern for 28, since you saw a haflaga of 28 days three times in a row (tishrei, cheshvon, kislev). Therefore, this month you need to keep haflaga of 28 by day (the established pattern you had), plus you need to keep both the haflaga and yom chodesh of your most recent vest (35 days plus whichever day of the month it was).
[Whether you need to keep the onah beinois or not it’s a dispute among the poskim, however since last month had only 29 days, it is not relevant in your case, since it is the same day as yom hachodesh.]