You got asked for a citation for your claim. Saying "look it up" is a tactic used by children. Congratulations on undermining your own (already flimsy) argument that humans are not monogamous.

As you said, get fucked.

you can find the proof for yourself. do a little research on anthropology

You have made a bold claim. Therefore, it would be beneficial to support it. Otherwise it's just hot air.

also see the high prevalence of cheating across romantic relationships

I suppose there is also a high prevalence of loyal behaviour across romantic relationships. But even if not, you are making to mistakes here imo:

1. Prevalence of something does not necessarily constitute "natural" behaviour. Depending on the specific numbers of this prevalence and how specifically it is defined. Especially, given that many things in biology are of rather statistical nature.
2. You are using that as an argument to justify moral behaviour. Even if it were true (which you refused to provide proof for so far), just because something is natural, it is not necessarily "good". See also: Appeal to nature.
   (Edit: to avoid misconceptions: I am referring to your previous comment where you basically said "duh, ofc they are cheating, it is natural. Also: monogamy is a curse by evil rich people". I am not saying that anyone implies moral superiority of monogamy over polygamy or the other way around.)

or maybe you prefer to ignore that because its inconvenient to your position

No, to the contrary. I am always open for good and factually based arguments. It's never wrong to correct one's stance given better information. So, feel invited to share your knowledge.

just because you personally are fine with your personal monogamous situation doesnt mean that humans are naturally monogamous

Correct. And my argument was based on rather anectodal evidence. However, given that I find that not only in my relationship, but also in others, suggests that humans are possibly not as easy to shove into a single drawer with regard to monogamy. But I didn't do the deep dive and do not have the numbers. However, since I do not experience this as a rarity, this provides ground for contradicting your claim.

hell your partner might not really be ok with it. for all you know they might just be keeping up appearances

Given that I literally talked with my partner about the possibility of opening up our relationship in case they feel the need to, this would be a really unnecessary and odd thing to do. ;)

theres plenty of evidence to support that we arent monogamous

Feel free to share this evidence, I am interested. :)

but to be honest youre not worth trying to convince

I wonder whether this is your default reaction to people who challenge your opinions and claims. If you allow, I suggest thinking about that in case you're looking for civil and constructive discussions.

maybe you could read up on the history of marriage to see what i mean. monogamous marriage exists primarily to handle the inheritance of wealth, which is something that really only matters to rich people who have something worth inheriting

Marriage did have that as primary use a long time ago, yes. But times have changed, as have the meanings around marriage. Given how marriage has been more of a rather formal institution back then, this is, imo, only a weak indicator for true monogamy or true polygamy. One could be married and be either of those. As it is the case today as well. Furthermore, nowadays, you also do not need to be married to manage inheritance. So while it has often been the case back then, it isn't today.

you still cant have a marriage between more than 2 people, or marry more than one person, let alone more complex arrangements

According to a brief read of Wikipedia, there are 58 countries where you can have polygamous marriages. Link

I think it is important to make a distinction here, because it seems you are partly mixing up forms of marriage with the innate individual preference for monogamous or polygamous relationships. But the form of marriage does not necessarily tell about this preference. So just because someone has a monogamous relationship, e.g., in form of a marriage, doesn't mean they really monogamous. Same thing with polygamy: people can be unhappy in polygamous constellations because they are actually monogamous.

in most places thats explicitly illegal. so yeah none of us really have a say

That is true and unfortunate and hopefully we, as humans worldwide, will advance to become more open to the legal status of polygamous relationships. In many places, we're making progress on that front. Moreover, although you can not legally marry more than one person in most countries, a lot of countries still tolerate polygamous relationships and do not prosecute them.
But again, we are mixing things here.

And we haven't even put a distinction between sexual and romantic preferences into the equation yet.