So first off, your question is mostly confused by your mishearings (see aguijonazo's comment). That said, the basic question can still be answered.
First, we need to talk about the pitch accents of the individual words (which I choose to use downstep notation for because the actual per-mora pitch is not realized yet until we put it into sentences which I will do later):
- 僕 allows for two patterns, ぼ\く and ぼく ̄.
- こと is generally こと\, however in some cases it is said こ\と, especially when proceeded by a heiban word and not followed by a particle (e.g., やったこ\とない). In addition to those cases, younger speaker sometimes say it こ\と even in the presence of a particle, but it is still a minority accent. (It may eventually switch fully to atamadaka like the grammar element と\き did, but it hasn't yet).
Then, on top of the standalone pitch accents, when words combine into a phrase, you need to consider phrase-level phenomenon (what accents get terraced or eliminated), which then further gets sentence-level phenomenon (e.g., are you emphasizing any of the entire phrases, is there 語尾上げ, are there questions, etc.)
1
For example, if we choose ぼ\く and こと\ as our accents, this could potentially manifest as:
- A. No terracing: ぼくのことは{HLLLHL}
- B. Terracing of the second accent: [ぼ]{H}[く]{L}[の]{L}[こ]{L}[と]{M}[は]{L} (we don't have line notation for M, sorry)
- C. Full elimination of the second accent: ぼくのことは{HLLLLL}
The first option would sound like こと is emphasized (which is weird in this type of phrase), while the second option would sound neutral, and the third option would sound like 僕 is emphasized.
2
We could also pick ぼく ̄ and こと\ as our accents, which would result in the two options
- A. Stay high: ぼくのことは{LHHHHL}
- B. Drop down for こ: ぼくのことは{LHHLHL}
Both are acceptable, but the lower you drop the こ, the more the word will stick out, and in some sense sound emphasized, distinct, or if you go too far, weird.
3
Alternatively, we could pick ぼく ̄ and こ\と as our accents, then the only option would be
ぼくのこと{LHHHL}(どう思っている?)
This only covers some of the combinations, but hopefully you get the idea of some of the complexity when you consider all of
- multiple accents at the word-level (pitch accents),
- multiple ways intonation-wise for the words to be combined at the phrase-level,
- multiple ways intonation-wise for the phrases to get integrated at the sentence-level.