Regex Split Match AND Group [duplicate]

I've a little regex (\d\.){2,} to split Chapters of a Book. The Chapters are recognized as a single digit followed by a dot and this combination occures at least twice. It should just split Chapters no single listings. Here's an example:

3.2.4.2. porta pellentesque   
139. Nunc maximus maximus aliquet? 
 a) dignissim 
 b) volutpat  
 c) ullamcorper  

3.2.4.3. ligula at condimentum fringilla  
152. Sed dapibus nulla mi, id lobortis ligula bibendum vehicula?  
 a) vestibulum   
 b) pellentesque   
 c) tempus   
 d) rutrum   
 
153. Lorem ipsum dolor sit amet. Sed iaculis lacus pellentesque, non auctor eros lobortis?  
 a) suscipit   
 b) vulputate   
 c) vestibulum   
 d) congue   
 
3.2.5. elementum quis  

It should be split at 3.2.4.2., 3.2.4.3. and 3.2.5. The regex Builder recognize the correct match but it always add an unwanted group match at the end and i don't get rid of that. The result looks like (one Bullet is one split):

• 3.2.4.
• 2.
• ...

---

• 3.2.4.
• 3.
• ...

---

• 3.2.
• 5.
• ...

I want it to be three splits not nine. I tried it with greedy/lazy quantifiers, various encapsulations but unfortunately I didn't get it right. What may be worth mentioning is that the whole thing should run in a python project. For a better understanding here is the link to the regexbuilder I used.